A multi-condition air preheater anti-clogging system

Abstract

This utility model discloses a multi-condition air preheater anti-clogging system, comprising: a rotary air preheater, a tubular air preheater, a primary air fan, a forced draft fan, a cold air electric shut-off valve, a bypass flue gas electric shut-off valve, a compensator, a flue gas bypass pipeline, a tube box, electric heating rods, and a metal wire plate. The heat source is drawn from the flue gas pipeline after the SCR denitrification unit or the inlet flue gas pipeline of the rotary air preheater, and is used to calcine the tubular air preheaters in groups, reducing air leakage rate and system fan power consumption, and improving boiler combustion efficiency. Simultaneously, electric heating rods are installed in the tube box, which can effectively increase the air preheater temperature when the unit is operating at low load and the flue gas temperature is low, causing ABS to decompose and volatilize, thereby inhibiting the formation of ammonium bisulfate in the air preheater, reducing clogging, and improving system operational stability.

Description

Technical Field

[0001] This utility model belongs to the field of air preheaters, specifically relating to an air preheater anti-clogging system under multiple operating conditions. Background Technology

[0002] An air preheater, also known as an air heat exchanger, is a heat exchange device that utilizes the waste heat from the flue gas at the boiler's tail end to heat the air needed for boiler combustion, thereby reducing heat loss during flue gas exhaust and improving the overall efficiency of the boiler. Air preheaters are mainly classified into plate type, rotary type, and tubular type. Among these, clogging of rotary air preheaters has always been a key factor affecting the normal operation of the equipment. Clogging in rotary air preheaters is mainly due to the reaction between escaped ammonia from the SCR denitrification system and SO3 in the flue gas produced by coal combustion in coal-fired boilers, generating ammonium sulfate and ammonium bisulfate (ABS). Simultaneously, some SO2 in the inlet flue gas is also oxidized to SO3 under the action of a catalyst, further increasing the formation of these two substances. Ammonium bisulfate is liquid at 147~230℃ and has strong viscosity, easily adhering to the surface of the heat storage elements at the cooling end of the rotary air preheater, and also adhering to fly ash in the flue gas, causing clogging of the air preheater.

[0003] With the vigorous development of new energy sources, thermal power turbines, which are used as peak-shaving power sources, have been operating at low loads and in a deep peak-shaving manner for a long time, which has further aggravated the blockage of air preheaters.

[0004] The existing patented technology adds a tubular heat exchanger between the rotary air preheater and the dust collector, thereby increasing the inlet cold air temperature of the rotary air preheater and transferring the risk of ABS deposition to the tubular heat exchanger. At the same time, hot air is used to locally heat the tubular heat exchanger, raising the metal wall temperature to 210°C, causing the surface ABS to volatilize.

[0005] However, using hot air as a heat source to calcine the tubular heat exchanger has several drawbacks. First, it increases the air leakage rate in the air system, leading to increased fan power consumption. Second, it reduces the amount of hot air required for boiler combustion, resulting in decreased overall boiler efficiency. Furthermore, at low unit loads, the hot air temperature is low, and ABS requires temperatures of 250°C or higher to volatilize and prevent further deposition, causing blockage in the tubular heat exchanger. Utility Model Content

[0006] The technical problem to be solved by this utility model is to solve the blockage of the ABS in the tubular air preheater. In order to solve the above problem, an air preheater anti-blockage system under multiple operating conditions is provided.

[0007] The objective of this utility model is achieved in the following manner: A multi-condition air preheater anti-clogging system includes a rotary air preheater 1, a tubular air preheater 2, a primary air fan 3, a blower 4, a cold air electrically shut-off valve 5, a hot flue gas bypass electrically shut-off valve 6, a compensator 7, and a hot flue gas bypass pipeline 8. The rotary air preheater 1 is connected to an upstream SCR denitrification unit and a downstream tubular air preheater 2 via a flue gas pipeline on its flue gas side. The rotary air preheater 1 is connected to the outlet of the tubular air preheater 2 via a duct. The air-side inlet of the tubular air preheater 2 is divided into functional zones via cold air ducts. The primary air fan 3 and the blower 4 are not connected separately; the air-side outlet of the tubular air preheater 2 is connected to the air-side inlet of the rotary air preheater 1 through a warm air duct according to the functional zone; the cold air duct at the inlet of the tubular air preheater 2 is equipped with a cold air electric shut-off valve 5 to block the flow medium; the hot flue gas bypass pipeline 8 is led out from the flue gas duct after the SCR denitrification device or the flue gas duct at the inlet of the rotary air preheater 1 and connected to the flue gas inlet of the tubular air preheater 2; the hot flue gas bypass pipeline 8 is equipped with a hot flue gas bypass electric shut-off valve 6 and a compensator 7.

[0008] The tubular air preheater 2 is arranged on the vertical flue gas duct at the outlet of the rotary air preheater 1 or on the horizontal or vertical flue gas duct leading into the dust collector.

[0009] The tubular air preheater 2 includes several sets of tube boxes 10. Each set of tube boxes 10 is equipped with an upper tube sheet 22a, a middle tube sheet 22b, and a lower tube sheet 25. Multiple heat exchange tubes 20 and metal sleeves 24 are evenly arranged inside the tube box 10. The metal sleeves 24 and heat exchange tubes 20 are arranged in a staggered manner. The outer part of the metal sleeve 24 is provided with a castable material 21 at the junction with the top of the upper tube sheet 22a to prevent the flue gas from eroding and corroding the metal sleeve. The lower tube sheet 25 is hollow inside. The top of the lower tube sheet 25 is connected to the metal sleeve 24, and the bottom of the lower tube sheet 25 is connected to the heat exchange tubes 20. The interior is equipped with a parallel metal wire plate 26 for energizing the heating rods 23 with "+" and "-" poles. The metal wire plate 26 is connected to the main terminal 27.

[0010] The system also includes a temperature detection device and a system temperature control device installed on the pipe wall of the pipe box.

[0011] The beneficial effects of this invention are as follows: This invention addresses the issue of ABS blockage in tubular air preheaters by drawing heat sources (approximately 300-400℃) from the flue gas duct after the SCR denitrification unit or the inlet flue gas duct of the rotary air preheater. This group heating of the tubular air preheater avoids interference with the air system required for boiler combustion, reduces air leakage and system fan power consumption, and improves boiler combustion efficiency. Simultaneously, group heating reduces the amount of bypass flue gas used at one time, allowing for smaller bypass flue gas duct diameters and saving investment. Electric heating rods installed inside the tube box effectively increase the air preheater temperature when the unit is operating at low load and the flue gas temperature is low, causing ABS to decompose and volatilize, thereby inhibiting the formation of ammonium bisulfate in the air preheater and reducing blockage. With the electric heating activated, the temperature can be adjusted at any time, unaffected by unit load. The electric heating rod device can be periodically activated during low-load peak shaving or when spot market electricity prices are low, heating the flue gas side temperature to 250-300℃, simultaneously accelerating the decomposition of the blockage-causing ammonium bisulfate. Attached Figure Description

[0012] Figure 1 This is a system schematic diagram of this utility model.

[0013] Figure 2 This is a diagram of the tube box of this utility model.

[0014] Figure 3 yes Figure 2 Detailed layout diagram.

[0015] Among them, 1-rotary air preheater; 2-tubular air preheater; 3-primary air fan; 4-forced air fan; 5-cold air electric shut-off valve; 6-hot flue gas bypass electric shut-off valve; 7-compensator; 8-hot flue gas bypass pipeline; 10-tube box; 20-heat exchange tube; 21-castable material; 22a-upper tube sheet; 22b-middle partition plate; 23-electric heating rod; 24-metal sleeve; 25-lower tube sheet; 26-metal wire plate; 27-main terminal block. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0017] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same technical meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0018] like Figure 1 As shown, a multi-condition air preheater anti-clogging system includes a rotary air preheater 1, a tubular air preheater 2, a primary air fan 3, a blower 4, a cold air electric shut-off valve 5, a hot flue gas bypass electric shut-off valve 6, a compensator 7, and a hot flue gas bypass pipeline 8.

[0019] The hot end of the rotary air preheater 1 is connected to the upstream SCR denitrification device through a flue gas pipeline, receiving high-temperature flue gas from the SCR denitrification device. The downstream end is connected to the tubular air preheater 2, providing the tubular air preheater 2 with waste heat from the flue gas that needs to be heated.

[0020] The air side (cold end) of the rotary air preheater 1 is connected to the outlet of the tubular air preheater 2 via a duct; the air side inlet of the tubular air preheater 2 is connected to the primary air fan 3 and the blower 4 respectively via cold air ducts according to the functional zones; the flue gas-air heat exchange is carried out through the heat exchange tubes 20 in the tube box 10, thereby providing warm air to the rotary air preheater, and the rotary air preheater 1 further exchanges heat with the warm air through the internal heat storage elements, so that it reaches the temperature required for boiler combustion.

[0021] The air-side outlet of the tubular air preheater 2 is connected to the air-side inlet of the rotary air preheater 1 via a warm air duct according to the functional zones; the cold air duct at the inlet of the tubular air preheater 2 is equipped with a cold air electric shut-off valve 5 to block the flow medium; the hot flue gas bypass pipe 8 is led out from the flue gas duct after the SCR denitrification device or the flue gas duct at the inlet of the rotary air preheater 1 and connected to the flue gas inlet of the tubular air preheater 2 to heat the ammonium bisulfate adhering to the heat exchange tube 20.

[0022] The hot flue gas bypass pipeline 8 is equipped with a hot flue gas bypass electric shut-off valve 6 and a compensator 7.

[0023] The tubular air preheater 2 is arranged on the vertical flue gas duct at the outlet of the rotary air preheater 1 or on the horizontal or vertical flue gas duct leading into the dust collector.

[0024] like Figure 2 and Figure 3 As shown, the tubular air preheater 2 includes several sets of tube boxes 10. Each set of tube boxes 10 is provided with an upper tube sheet 22a, a middle tube sheet 22b, and a lower tube sheet 25. Multiple heat exchange tubes 20 and metal sleeves 24 are evenly arranged inside the tube box 10. The metal sleeves 24 and heat exchange tubes 20 are arranged in a staggered manner. The recessed part at the junction of the metal sleeve 24 and the top of the upper tube sheet 22a is provided with castable material 21 or fire-resistant and corrosion-resistant filler to prevent the flue gas from eroding and corroding the metal sleeve. The lower tube sheet 25 is hollow inside. The top of the lower tube sheet 25 is connected to the metal sleeve 24, and the bottom of the lower tube sheet 25 is connected to the heat exchange tubes 20. The interior is provided with a parallel metal wire plate 26 for energizing the heating rods 23 with "+" and "-" poles. The metal wire plate 26 is connected to the main terminal 27.

[0025] The system also includes a temperature detection device and a system temperature control device installed on the pipe wall of the pipe box.

[0026] The specific engineering process is as follows: When the system is operating normally, the flue gas flows from left to right through: SCR denitrification unit (flue gas temperature 300~400℃) — rotary air preheater 1 (160~200℃) — tubular air preheater 2 (80~120℃) — downstream. The air flows from right to left through: primary air fan 3, forced draft fan 4 (20~40℃) — tubular air preheater 2 (90~120℃) — rotary air preheater 1 (280~380℃). Heat exchange occurs between the flue gas and air in rotary air preheater 1 and tubular air preheater 2.

[0027] When the pressure difference between the inlet and outlet of the tubular air preheater 2 is detected to exceed the normal design range, indicating severe blockage, the cold air electric shut-off valve 5 is closed sequentially, and the bypass flue gas electric shut-off valve 6 is opened to allow high-temperature flue gas of approximately 300~400℃ to enter the tubular air preheater 2 through the hot flue gas bypass pipe 8, raising the temperature of the tube box 10 to above 250℃. This process continues until the ABS thermal decomposition is complete, at which point the bypass flue gas electric shut-off valve 6 is closed, and the cold air electric shut-off valve 5 is opened. This is repeated for one group at a time. During the heating process, if the tube box wall temperature measuring device detects a temperature below 147℃ for an extended period (when the unit is operating at low load and the flue gas temperature is low), the system temperature control device activates the electric heating device. Current flows through the main terminal 27 and metal plate 26 into the electric heating rod 23, converting electrical energy into heat energy, which heats the entire tube box and promotes the decomposition of ammonium bisulfate.

[0028] This invention addresses the issue of ABS blockage in tubular air preheaters by drawing heat from the flue gas duct after the SCR denitrification unit or the inlet flue gas duct of the rotary air preheater (temperature approximately 300-400℃). This group heating of the tubular air preheater avoids interference with the air system required for boiler combustion, reduces air leakage and system fan power consumption, and improves boiler combustion efficiency. Simultaneously, group heating reduces the amount of bypass flue gas used at one time, allowing for a smaller bypass flue gas duct diameter and saving investment. Electric heating rods are installed inside the tube box. When the unit operates at low load and the flue gas temperature is low, this effectively increases the air preheater temperature, causing ABS to decompose and volatilize, thereby inhibiting the formation of ammonium bisulfate in the air preheater and reducing blockage. With the electric heating activated, the temperature can be adjusted at any time, unaffected by unit load. The electric heating rod device can be periodically activated during low-load peak shaving or when spot market electricity prices are low, heating the flue gas side temperature to 250-300℃, simultaneously accelerating the decomposition of the blockage-causing ammonium bisulfate.

[0029] The above description is only a preferred embodiment of the present utility model. It should be noted that those skilled in the art can make several changes and improvements without departing from the overall concept of the present utility model, and these should also be considered within the protection scope of the present utility model.

Claims

1. A multi-condition air preheater anti-clogging system, characterized in that: The system includes a rotary air preheater (1), a tubular air preheater (2), a primary air fan (3), a blower (4), a cold air electric shut-off valve (5), a hot flue gas bypass electric shut-off valve (6), a compensator (7), and a hot flue gas bypass pipeline (8). The rotary air preheater (1) is connected to the upstream SCR denitrification unit and the downstream tubular air preheater (2) via a flue gas pipeline on the flue gas side. The rotary air preheater (1) is connected to the outlet of the tubular air preheater (2) via a duct. The air inlet of the tubular air preheater (2) is connected to the primary air preheater via a cold air duct according to the functional zones. The air preheater (2) is connected to the air inlet of the rotary air preheater (1) through a warm air duct according to the functional zone. The cold air duct at the inlet of the tubular air preheater (2) is equipped with a cold air electric shut-off valve (5) to block the flow medium. The hot flue gas bypass pipe (8) is led out from the flue after the SCR denitrification device or the flue at the inlet of the rotary air preheater (1) and connected to the flue gas inlet of the tubular air preheater (2). The hot flue gas bypass pipe (8) is equipped with a hot flue gas bypass electric shut-off valve (6) and a compensator (7).

2. The air preheater anti-clogging system under multiple operating conditions according to claim 1, characterized in that: The tubular air preheater (2) is arranged on the vertical flue gas duct at the outlet of the rotary air preheater (1) or on the horizontal or vertical flue gas duct leading to the dust collector.

3. The air preheater anti-clogging system under multiple operating conditions according to claim 1, characterized in that: The tubular air preheater (2) includes several sets of tube boxes (10). Each set of tube boxes (10) is provided with an upper tube sheet (22a), a middle tube sheet (22b), and a lower tube sheet (25). Multiple heat exchange tubes (20) and metal sleeves (24) are evenly arranged inside the tube boxes (10). The metal sleeves (24) and heat exchange tubes (20) are arranged in a staggered manner. The outer part of the metal sleeve (24) is provided with a castable material (21) at the junction with the top of the upper tube sheet (22a) to prevent the flue gas from eroding and corroding the metal sleeve. The lower tube sheet (25) is hollow inside. The top of the lower tube sheet (25) is connected to the metal sleeve (24), and the bottom of the lower tube sheet (25) is connected to the heat exchange tubes (20). The interior is provided with a parallel metal wire plate (26) for energizing the electric heating rod (23). The metal wire plate (26) is connected to the main terminal (27).

4. The air preheater anti-clogging system under multiple operating conditions according to claim 1, characterized in that: The system also includes a temperature detection device and a system temperature control device installed on the pipe wall of the pipe box.

Images