A heating device for denitrification dilution air system

Abstract

The present invention discloses a heating device for a denitrification dilution air system. The heating device is installed in the economizer outlet flue or the low-temperature superheater inlet flue. The heating device includes multiple branch pipes, one outlet end of each branch pipe is located in the economizer outlet flue or the low-temperature superheater inlet flue, and the heating device includes heating branches. By installing a heating device for heating the dilution air in the economizer outlet flue or the low-temperature superheater inlet flue, the present invention uses the heat of the high-temperature flue gas as the heating source, which not only facilitates long-term safe and stable operation, but also avoids problems such as dust accumulation and blockage, effectively solving the heating problem of the denitrification dilution air.

Description

Technical Field

[0001] The invention relates to a heating device for a denitration dilution air system, belonging to the technical field of denitration and energy saving. Background Art

[0002] SCR (Selective Catalytic Reduction) technology is the most advanced, mature and reliable flue gas denitrification technology in the field of boiler nitrogen oxide removal technology in China. X The fundamental reducing reactants of the reaction directly influence the choice of denitrification process route. Technologies using liquid ammonia and urea as reducing agents are widely used. The "Technical Specification for Flue Gas Denitrification Design in Thermal Power Plants" (DL / T 5480-2013) clearly stipulates: "The ammonia concentration at the outlet of the auxiliary system ammonia / air mixer shall not exceed 5% (volume fraction)." Therefore, properly controlling the dilution air volume is crucial.

[0003] The denitrification system that uses liquid ammonia evaporated gas as a reducing agent adopts dilution air at normal temperature and pressure as dilution air when mixing ammonia / air. The dilution air temperature is relatively low (about 20°C). After the denitrification system has been running for a period of time, due to the influence of temperature difference, ammonium bisulfate crystals will precipitate at the nozzle of the ammonia injection grid. Combined with the high-ash wet flue gas, the nozzle will gradually be blocked, which will directly affect the denitrification efficiency, ammonia escape rate, ammonia consumption and the distribution of NH3 concentration field, and indirectly have a negative impact on the dust accumulation of downstream catalysts and the blockage of air preheaters.

[0004] In a denitrification system that uses urea hydrolysis to produce ammonia as a reducing agent, the product gas needs to be transported with heat (around 160°C). When ammonia / air is mixed, hot primary air / secondary air is often used as dilution air. For some renovation projects, the boiler's hot primary air / secondary air margin is small, and the existing blower needs to be modified. The hot primary air / secondary air will change with changes in boiler load; due to air leakage in the air preheater, dust in the flue gas will be mixed into the hot primary air / secondary air, and long-term operation will cause blockage or wear of the ammonia injection system pipeline.

[0005] Some R&D teams have also considered using heat exchangers to heat the dilution air, but the location and application prospects of the heat exchanger involve certain risks; the heat exchanger is arranged in the SCR inlet flue with a high flow rate, which causes serious wear and corrosion to the heat exchanger, and is not conducive to long-term safe and stable operation; the heat exchanger is arranged in the SCR outlet flue, and after the flue gas passes through the catalyst reaction, the by-product ammonium bisulfate will adhere to the surface of the heat exchanger, accumulating dust, reducing the heat exchange effect, disrupting the flow field, and increasing the system resistance, which fails to achieve the goal of energy saving and consumption reduction. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a heating device for a denitrification dilution air system.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A heating device for a denitrification dilution air system, the heating device is installed in the economizer outlet flue or in the low-temperature superheater inlet flue, the heating device includes an air inlet pipe, an air outlet pipe and a heat exchange device composed of multiple heating branches, the multiple heating branches are arranged between the air inlet pipe and the air outlet pipe, a first sealing section is provided between the air inlet pipe and the heat exchange device, a second sealing section is provided between the heat exchange device and the air outlet pipe, and one outlet end of the heating branch pipe is provided in the economizer outlet flue or the low-temperature superheater inlet flue.

[0009] The aforementioned heating device for a denitrification dilution air system is a tube bundle cross-flow heat exchanger.

[0010] The aforementioned heating device for a denitrification dilution air system is a plate-fin cross-flow heat exchanger.

[0011] The aforementioned heating device for a denitrification dilution air system, wherein the heating branch pipe is a W-shaped single-side inserted pipe, a U-shaped single-side inserted pipe, or an L-shaped single-side inserted pipe.

[0012] The aforementioned heating device for a denitrification dilution air system, wherein the heating branch pipe is a rectangular single-side inserted pipe, a corrugated single-side inserted pipe, a triangular single-side inserted pipe, or a serrated single-side inserted pipe.

[0013] The aforementioned heating device for a denitrification dilution air system is suspended on the lower frame structure beam of the economizer, and uses the side wall panel of the economizer outlet flue as a suspension support point.

[0014] The aforementioned heating device for a denitrification dilution air system further includes a high-temperature air manifold and a low-temperature air manifold. The heat exchange device composed of multiple heating branches is a single-loop pipe group structure. The single-loop pipe group structure is arranged between the high-temperature air manifold and the low-temperature air manifold. The high-temperature air manifold is arranged on the side wall panel of the economizer outlet flue.

[0015] The aforementioned heating device for a denitrification dilution air system is suspended on the upper frame structure beam of the low-temperature superheater, and uses the side wall plate of the low-temperature superheater inlet flue as a suspension support point.

[0016] The aforementioned heating device for a denitrification dilution air system further includes a high-temperature air manifold and a low-temperature air manifold. The heat exchange device composed of the multiple heating branches is a single-loop pipe group structure. The single-loop pipe group structure is arranged between the high-temperature air manifold and the low-temperature air manifold. The high-temperature air manifold is arranged on the side wall panel of the low-temperature superheater inlet flue.

[0017] The aforementioned heating device for a denitrification dilution air system, wherein the high-temperature air manifold is connected to a heat exchange device composed of multiple heating branch pipes, and the high-temperature air manifold is also connected to the air outlet pipe; the low-temperature air manifold is connected to a heat exchange device composed of multiple heating branch pipes, and the low-temperature air manifold is also connected to the air inlet pipe.

[0018] Compared with the existing technology, the present invention sets a heating device for heating the dilution air in the economizer outlet flue or installed in the low-temperature superheater inlet flue. The heat of the high-temperature flue gas is used as the heating source, which is conducive to long-term safe and stable operation, and does not have the problems of dust accumulation and blockage, and can effectively solve the heating problem of the denitrification dilution air. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute an undue limitation to the present invention. In the accompanying drawings:

[0020] Figure 1 It is a elevational layout diagram of the heating device of the present invention;

[0021] Figure 2 It is a plan layout diagram of the heating device of the present invention;

[0022] Figure 3 yes Figure 1 A magnified view of middle A;

[0023] Figure 4 It is a structural diagram of this utility model;

[0024] Figure 5 This is a schematic diagram of the structure of the heating device of the present invention installed in the economizer outlet flue;

[0025] Figure 6 yes Figure 5 Enlarged view of middle B;

[0026] Figure 7 It is a schematic diagram of the heating device structure of a single-loop pipe group.

[0027] Figure markings: 1-heating device, 101-air inlet pipe, 102-air outlet pipe, 103-heating branch pipe, 104-first sealing section, 105-second sealing section, 2-economizer outlet flue, 3-low-temperature superheater inlet flue, 4-economizer lower frame structure beam, 5-high-temperature air header, 6-low-temperature air header, 7-side wall panel of economizer outlet flue.

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0030] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or are inherent to these processes, methods, products or apparatus.

[0031] Embodiment 1 of the present invention: A heating device for a denitrification dilution air system, wherein the heating device 1 is installed in the economizer outlet flue 2 or in the low-temperature superheater inlet flue 3. The heating device 1 includes an air inlet pipe 101, an air outlet pipe 102, and a heat exchange device consisting of multiple heating branches 103. The multiple heating branches 103 are arranged between the air inlet pipe 101 and the air outlet pipe 102. A first sealing section 104 is provided between the air inlet pipe 101 and the heat exchange device, and a second sealing section 105 is provided between the heat exchange device and the air outlet pipe 102. One outlet end of the heating branch 103 is provided in the economizer outlet flue 2 or the low-temperature superheater inlet flue 3. The heating device 1 is a tube bundle cross-flow heat exchanger. The heating branch 103 is a W-shaped single-side inserted tube.

[0032] Embodiment 2 of the present invention: A heating device for a denitrification dilution air system, wherein the heating device 1 is installed in the economizer outlet flue 2 or in the low-temperature superheater inlet flue 3. The heating device 1 includes an air inlet pipe 101, an air outlet pipe 102, and a heat exchange device consisting of multiple heating branches 103. The multiple heating branches 103 are arranged between the air inlet pipe 101 and the air outlet pipe 102. A first sealing section 104 is provided between the air inlet pipe 101 and the heat exchange device, and a second sealing section 105 is provided between the heat exchange device and the air outlet pipe 102. One outlet end of the heating branch 103 is provided in the economizer outlet flue 2 or the low-temperature superheater inlet flue 3. The heating device 2 is a plate-fin cross-flow heat exchanger. The heating branch 103 is a U-shaped single-side inserted tube.

[0033] Embodiment 3 of the present invention: A heating device for a denitrification dilution air system. The heating device 1 is installed in the economizer outlet flue 2 or the low-temperature superheater inlet flue 3. The heating device 1 includes an air inlet duct 101, an air outlet duct 102, and a heat exchange device consisting of multiple heating branches 103. The multiple heating branches 103 are arranged between the air inlet duct 101 and the air outlet duct 102. A first sealing section 104 is provided between the air inlet duct 101 and the heat exchange device, and a second sealing section 105 is provided between the heat exchange device and the air outlet duct 102. One outlet end of the heating branch 103 is located in the economizer outlet flue 2 or the low-temperature superheater inlet flue 3. The heating device 1 is a tube bundle cross-flow heat exchanger. The heating branches 103 are L-shaped, rectangular, corrugated, triangular, or zigzag single-side inserted tubes.

[0034] Embodiment 4 of the present invention: A heating device for a denitrification dilution air system, wherein the heating device 1 is installed in the economizer outlet flue 2. The heating device 1 includes an air inlet pipe 101, an air outlet pipe 102, and a heat exchange device consisting of multiple heating branches 103. The multiple heating branches 103 are arranged between the air inlet pipe 101 and the air outlet pipe 102. A first sealing section 104 is provided between the air inlet pipe 101 and the heat exchange device, and a second sealing section 105 is provided between the heat exchange device and the air outlet pipe 102. One outlet end of the heating branch 103 is provided in the economizer outlet flue 2. The heating device 1 is suspended from the economizer lower frame structure beam 4, and the side wall panel 7 of the economizer outlet flue serves as a suspension support point. The heating device 1 also includes a high-temperature air header 5 and a low-temperature air header 6. The heat exchange device formed by the multiple heating branches 103 is a single-circuit pipe group structure, which is installed between the high-temperature air header 5 and the low-temperature air header 6. The high-temperature air header 5 is installed on the side wall 7 of the economizer outlet flue. The high-temperature air header 5 is connected to the heat exchange device formed by the multiple heating branches 103 and is also connected to the air outlet pipe 102. The low-temperature air header 6 is also connected to the heat exchange device formed by the multiple heating branches 103 and is also connected to the air inlet pipe 101. In this example, the heating device is manufactured using Q345B steel.

[0035] Embodiment 5 of the present invention: A heating device for a denitrification dilution air system, wherein the heating device 1 is installed in the low-temperature superheater inlet flue 3. The heating device 1 includes an air inlet pipe 101, an air outlet pipe 102, and a heat exchange device consisting of multiple heating branches 103. The multiple heating branches 103 are arranged between the air inlet pipe 101 and the air outlet pipe 102. A first sealing section 104 is provided between the air inlet pipe 101 and the heat exchange device, and a second sealing section 105 is provided between the heat exchange device and the air outlet pipe 102. One outlet end of the heating branch 103 is provided in the low-temperature superheater inlet flue 3. The heating device 1 is suspended from the upper frame structure beam of the low-temperature superheater, and the side wall panel of the low-temperature superheater inlet flue 3 serves as a suspension support point. The heating device 1 also includes a high-temperature air header 5 and a low-temperature air header 6. The heat exchange device, consisting of multiple heating branches 103, is a single-circuit pipe group structure, located between the high-temperature air header 5 and the low-temperature air header 6. The high-temperature air header 5 is mounted on the sidewall of the low-temperature superheater inlet flue 3. The high-temperature air header 5 is connected to the heat exchange device, consisting of multiple heating branches 103, and is also connected to the air outlet duct 102. The low-temperature air header 6 is also connected to the heat exchange device, consisting of multiple heating branches 103, and is also connected to the air inlet duct 101. In this example, the heating device is manufactured using SS304 steel.

[0036] Working principle of the present invention:

[0037] The high-temperature flue gas flow of the denitrification system passes through the outside of the heating device 1, and the denitrification dilution air enters from the air inlet pipe 101 of the heating device 1, and enters each heating branch pipe 103 after passing through the first air outlet section 104. The heat of the high-temperature flue gas is used as a heat source for heating the denitrification dilution air in the heating branch pipe 103. When the high-temperature flue gas passes through the heating device 1, the high-temperature flue gas and the denitrification dilution air exchange heat in a vertical cross direction. The denitrification dilution air heated in the heating branch pipe 103 passes through the second air outlet section 105 and is discharged from the air outlet pipe 102 of the heating device 1. Denitrification dilution air first enters the low-temperature air header 6 through the air inlet pipe 101. The low-temperature air header 6 is equipped with multiple rows of parallel pipes or serpentine pipes. The denitrification dilution air exchanges heat with the high-temperature flue gas at the low-temperature air header 6. The heated denitrification dilution air is further heated by the heat exchange device composed of multiple heating branch pipes 103 before being collected into the high-temperature air header 5. Finally, the heated denitrification dilution air is discharged through the air outlet pipe 102 and transported to subsequent equipment. The present invention has a simple structure and solves the heating problem of the denitrification dilution air by fully utilizing the heat of the high-temperature flue gas in the denitrification system. By using the present invention to heat the denitrification dilution air, the long-term safe and stable operation of the denitrification system can be guaranteed, and dust accumulation and blockage problems can be avoided.

Claims

1. A heating device for a denitrification dilution air system, characterized in that: The heating device (1) is installed in the economizer outlet flue (2) or in the low-temperature superheater inlet flue (3). The heating device (1) comprises an air inlet pipe (101), an air outlet pipe (102) and a heat exchange device consisting of a plurality of heating branch pipes (103). The plurality of heating branch pipes (103) are arranged between the air inlet pipe (101) and the air outlet pipe (102). A first sealing section (104) is provided between the air inlet pipe (101) and the heat exchange device, and a second sealing section (105) is provided between the heat exchange device and the air outlet pipe (102). One outlet end of the heating branch pipe (103) is provided in the economizer outlet flue (2) or the low-temperature superheater inlet flue (3). The heating device (1) is a tube bundle cross-flow heat exchanger or a plate-fin cross-flow heat exchanger. The heating branch pipe (103) is a W-shaped single-side inserted tube, a U-shaped single-side inserted tube, or an L-shaped single-side inserted tube.

2. A heating device for a denitrification dilution air system according to claim 1, characterized in that: The heating device (1) is suspended on the lower frame structure beam (4) of the economizer, and uses the side wall plate (7) of the economizer outlet flue (2) as a suspension support point.

3. The heating device for a denitrification dilution air system according to claim 2, characterized in that: The heating device (1) further comprises a high-temperature air header (5) and a low-temperature air header (6); the heat exchange device formed by the plurality of heating branch pipes (103) is a single-circuit pipe group structure, the single-circuit pipe group structure is arranged between the high-temperature air header (5) and the low-temperature air header (6); the high-temperature air header (5) is arranged on the side wall plate (7) of the economizer outlet flue (2).

4. The heating device for a denitrification dilution air system according to claim 1, characterized in that: The heating device (1) is suspended on the upper frame structure beam of the low-temperature superheater, and the side wall plate of the low-temperature superheater inlet flue (3) is used as a suspension support point.

5. The heating device for a denitrification dilution air system according to claim 4, characterized in that: The heating device (1) further comprises a high-temperature air header (5) and a low-temperature air header (6); the heat exchange device formed by the plurality of heating branch pipes (103) is a single-circuit pipe group structure; the single-circuit pipe group structure is arranged between the high-temperature air header (5) and the low-temperature air header (6); the high-temperature air header (5) is arranged on a side wall plate of the low-temperature superheater inlet flue (3).

6. A heating device for a denitrification dilution air system according to claim 3 or 5, characterized in that: The high-temperature air header (5) is connected to a heat exchange device consisting of a plurality of heating branch pipes (103), and the high-temperature air header (5) is also connected to the air outlet pipe (102); the low-temperature air header (6) is connected to a heat exchange device consisting of a plurality of heating branch pipes (103), and the low-temperature air header (6) is also connected to the air inlet pipe (101).

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