Dust deposition corrosion prevention device for industrial boiler SCR reactor outlet waste heat recovery heat exchanger

Abstract

An industrial boiler SCR reactor outlet waste heat recovery heat exchanger ash deposition corrosion prevention device comprises a medium-temperature-section ND steel light pipe type heat exchange pipe set, a low-temperature-section ND steel light pipe type heat exchange pipe set, a shock wave soot blower and a heat exchanger water inlet heat mixing and temperature adjusting system. The medium-temperature section ND steel light pipe type heat exchange pipe set is arranged on the upper portion of the low-temperature section ND steel light pipe type heat exchange pipe set, and the shock wave soot blower is located at the position 300-450 mm away from the uppermost row of pipes of the low-temperature section ND steel light pipe type heat exchange pipe set and arranged in front of a water inlet of the low-temperature section ND steel light pipe type heat exchange pipe set. The device has the characteristics that the device is resistant to sulfuric acid corrosion, the wall temperature of the heat exchange tube is higher than the water dew point of flue gas, and the shock wave ash removal device has strong ash removal capacity and is not easy to accumulate ash.

Description

Technical Field

[0001] This utility model relates to the field of boiler flue gas denitrification technology, specifically to a device for preventing ash accumulation and corrosion of the waste heat recovery heat exchanger at the outlet of an industrial boiler SCR reactor. Background Technology

[0002] The existing technology for outlet waste heat recovery heat exchangers in the SCR denitrification process has the following problems:

[0003] Existing all-smooth tube heat exchangers lack enhanced heat transfer capabilities, have numerous tube rows, are large in size, and occupy a lot of space. This makes them difficult to install in industrial boilers with limited outlet space for SCR reactors. They also consume a large amount of steel and are costly.

[0004] In waterless mixing and temperature control systems, the low-temperature section heat exchange tubes have low wall temperatures, making them prone to dust accumulation and corrosion.

[0005] After ash accumulation and corrosion in the low-temperature section, cleaning and maintenance become difficult. If a single heat exchange tube leaks due to ash accumulation and corrosion, emergency repairs require blindly plugging an entire row of heat exchange tubes, resulting in significant heat exchange area loss and making replacement of damaged pipes difficult.

[0006] Existing all-finned heat exchanger systems with inlet-type mixing and temperature control suffer from dust accumulation and corrosion in the low-temperature section due to the finned heat exchange structure. Once dust and corrosion occur in the low-temperature section, cleaning and maintenance become difficult. If a single heat exchange tube in the low-temperature section leaks due to dust and corrosion, emergency repairs require blindly plugging an entire row of heat exchange tubes, resulting in significant heat exchange area loss and difficulties in replacing damaged pipes.

[0007] The inlet water temperature of the heat exchanger is 45℃~50℃ low, causing the wall temperature of the low-temperature section of the waste heat recovery heat exchanger to be lower than the dew point of the boiler flue gas. The low-temperature section suffers from severe condensation and acid dew accumulation, leading to ash buildup and rapid corrosion. This ash accumulation and corrosion in the low-temperature section makes cleaning and maintenance difficult. Utility Model Content

[0008] In order to overcome the defects of easy ash accumulation and corrosion in the existing technology, this utility model proposes an anti-ash accumulation and corrosion device for the waste heat recovery heat exchanger at the outlet of the SCR reactor of an industrial boiler. The anti-corrosion device has the characteristics of being resistant to sulfuric acid corrosion, having a heat exchange tube wall temperature higher than the flue gas water dew point, strong ash removal ability of the shock wave soot remover, and being not prone to ash accumulation.

[0009] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0010] The anti-ash accumulation and corrosion device for the waste heat recovery heat exchanger at the outlet of the SCR reactor of an industrial boiler includes a medium-temperature section ND steel bare tube heat exchanger tube group 1, a low-temperature section ND steel bare tube heat exchanger tube group 2, a shock wave soot blower 3, and a heat exchanger inlet water mixing and temperature control system 4.

[0011] The medium-temperature section ND steel bare tube heat exchanger assembly 1 is installed above the low-temperature section ND steel bare tube heat exchanger assembly 2. The shock wave soot blower 3 is located 300-450mm from the top row of tubes in the low-temperature section ND steel bare tube heat exchanger assembly 2, and is installed before the water inlet of the low-temperature section ND steel bare tube heat exchanger assembly 2.

[0012] The heat exchanger inlet water mixing and temperature control system 4 is connected to the inlet water pipe of the low-temperature section ND steel bare tube heat exchanger tube group 2.

[0013] The heat exchanger inlet water mixing and temperature control system 4 is led out from the boiler outlet water header and connected to the heat exchanger inlet water pipe. It is used to increase the inlet water temperature of the low-temperature section ND steel bare tube heat exchanger tube group 2, prevent acid dew, and improve the service life of the heat exchanger.

[0014] The medium-temperature section ND steel bare tube heat exchanger tube assembly 1 and the low-temperature section ND steel bare tube heat exchanger tube assembly 2 are bare tube structures.

[0015] The medium-temperature section ND steel bare tube heat exchanger assembly 1 has 25 layers, and the low-temperature section ND steel bare tube heat exchanger assembly 2 has 5 layers.

[0016] The medium-temperature section ND steel bare tube heat exchanger tube group 1 is arranged in a serpentine pattern, and the low-temperature section ND steel bare tube heat exchanger tube group 2 is arranged in an S-shape.

[0017] The medium-temperature section ND steel bare tube heat exchanger assembly 1 is arranged in a serpentine pattern. Generally, in order to meet the heat exchange requirements, more than 20 layers of heat exchanger assemblies need to be arranged. The serpentine arrangement can save arrangement space.

[0018] The low-temperature section ND steel bare tube heat exchanger assembly 2 is arranged in an S-shape, and generally has a small number of layers, from 5 to 10, which facilitates maintenance and replacement of the heat exchanger assembly.

[0019] The medium-temperature section ND steel bare tube heat exchanger tube assembly 1 and the low-temperature section ND steel bare tube heat exchanger tube assembly 2 are directly connected through an intermediate header.

[0020] The heat exchanger inlet water mixing and temperature control system 4 draws a portion of hot water from the boiler outlet water pipe into the heat exchanger through a pipeline, thereby increasing the inlet water temperature of the heat exchanger. This ensures that the economizer tube wall temperature is higher than the flue gas water dew point during boiler operation, preventing severe ash accumulation and rapid corrosion of the low-temperature section heat exchange tubes.

[0021] Maintenance space is provided between the high-temperature section double H finned heat exchanger tube assembly and the medium-temperature section ND steel bare tube heat exchanger tube assembly 1, and between the medium-temperature section ND steel bare tube heat exchanger tube assembly 1 and the low-temperature section ND steel bare tube heat exchanger tube assembly 2. At the same time, an intermediate header is set between the medium-temperature section ND steel bare tube heat exchanger tube assembly 1 and the low-temperature section ND steel bare tube heat exchanger tube assembly 2 to facilitate inspection, cleaning and replacement of corroded and leaking heat exchanger tubes. If a single heat exchanger tube leaks, only the leaking heat exchanger tube needs to be blinded, avoiding short circuits of the entire heat exchanger tube row due to a single heat exchanger tube leak, which would cause a significant loss of heat exchanger area.

[0022] The shock wave soot blower 3 periodically and powerfully blows away the ash accumulation in the ND steel tube heat exchanger assembly 1 in the medium temperature section, preventing the liquid ammonium bisulfate (NH4HSO4) from bridging and blocking the flue gas passage between the heat exchanger tubes at the medium temperature end.

[0023] The heat exchanger inlet water mixing and temperature control system 4 mixes the water into the economizer to a temperature above 65°C, ensuring that the economizer tube wall temperature is higher than the flue gas water dew point during boiler operation, thus avoiding severe ash accumulation and rapid corrosion of the heat exchange tubes in the low-temperature section.

[0024] The heat exchanger inlet water mixing and temperature control system 4 consists of the connecting pipes and regulating valves between the boiler outlet water header and the heat exchanger inlet water pipe.

[0025] The beneficial effects of this utility model are:

[0026] This invention significantly alleviates the problem of dust accumulation and corrosion in SCR outlet heat exchangers, and extends the service life of the heat exchangers.

[0027] This utility model relates to a medium-temperature section ND steel bare tube heat exchanger assembly 1, which operates within a flue gas temperature range of 150℃ to 290℃. In this temperature range, ammonium bisulfate (NH4HSO4) in the flue gas is a viscous liquid. If it adheres to the heat exchanger tube wall, it will hydrolyze to release sulfuric acid and ammonia after the boiler shuts down and becomes damp. Therefore, the heat exchanger tubes are made of a bare tube structure that is not prone to ash accumulation and ND steel that is resistant to sulfuric acid corrosion. A powerful air-source shockwave soot blower 3 is installed at the top to periodically pulse-clean the heat exchanger tube assembly in the medium-temperature section, allowing the ammonium bisulfate mixed in the flue gas fly ash to be carried away by the flue gas, preventing accumulation and bridging between the heat exchanger tubes. The ND steel bare tube heat exchanger assembly 2 is located in a flue gas temperature range of 120℃ to 150℃. In this temperature range, ammonium bisulfate in the flue gas is a solid crystal and can be carried away by the flue gas with the ash. In the low-temperature range, the tube wall temperature is lower and the SO2 concentration in the flue gas is higher, which makes it easy for acid dew to form. The heat exchanger tubes are made of bare tube structure that is not easy to accumulate ash and ND steel material that is resistant to sulfuric acid corrosion. The front end of the inlet is equipped with a heat exchanger inlet water mixing and temperature regulation system 4 to increase the inlet water temperature, thereby increasing the tube wall temperature to above the acid dew point (80℃), avoiding ash accumulation and rapid corrosion of the heat tubes due to water dew and acid dew, and extending the service life of the heat exchanger. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the anti-ash accumulation and corrosion structure of the heat exchanger of this utility model.

[0029] Figure 2 This is a schematic diagram of the heat exchanger inlet water mixing and temperature control system of this utility model. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings.

[0031] like Figure 1 As shown, the heat exchanger anti-ash accumulation and corrosion structure of this utility model includes a medium-temperature section ND steel bare tube heat exchanger tube group 1, a low-temperature section ND steel bare tube heat exchanger tube group 2, and a shock wave soot blower 3.

[0032] The medium-temperature section bare tube heat exchanger assembly 1 operates within a flue gas temperature range of 150℃ to 290℃. Ammonium bisulfate in the flue gas is a viscous liquid within this temperature range. If it adheres to the heat exchanger tube wall, it will hydrolyze to release sulfuric acid and ammonia after shutdown and subsequent moisture buildup. Therefore, its heat exchanger tubes are made of a bare tube structure that is not prone to ash buildup and ND steel that is resistant to sulfuric acid corrosion. An air-source shockwave soot blower 3 with strong cleaning capabilities is installed at the top to periodically pulse-clean the medium-temperature heat exchanger assembly, allowing the ammonium bisulfate mixed in the flue gas fly ash to be carried away by the flue gas and prevent bridging between the heat exchanger tubes. The low-temperature section heat exchanger assembly 2 operates within a flue gas temperature range of 120℃ to 150℃. Ammonium bisulfate in the flue gas is a solid crystal within this temperature range and can be carried away by the flue gas along with the fly ash. The low-temperature section has a lower tube wall temperature, and when the SO2 concentration in the flue gas is higher, acid condensation is likely to form. Its heat exchanger tubes are also made of a bare tube structure that is not prone to ash buildup and ND steel that is resistant to sulfuric acid corrosion.

[0033] like Figure 2 As shown, a heat exchanger inlet water mixing and temperature control system 4 is configured at the front end of the heat exchanger inlet. It consists of a connecting pipe and a regulating valve between the boiler outlet water (90℃~130℃) main pipe and the heat exchanger inlet water pipe. It draws some boiler outlet water to mix and raise the heat exchanger inlet water temperature to above 65℃, thereby raising its pipe wall temperature to above the acid dew point (80℃), avoiding ash accumulation and rapid corrosion of the heat pipe, and extending the service life of the heat exchanger.

[0034] The working principle of this utility model:

[0035] This utility model discloses a system for preventing ash accumulation and corrosion of the waste heat recovery heat exchanger at the outlet of an industrial boiler SCR reactor, including a heat exchanger anti-ash accumulation and corrosion structure and a heat exchanger inlet water mixing system structure.

[0036] The heat exchanger is designed to prevent dust accumulation, and a mixing system for the inlet water is used to raise the inlet water temperature, thereby increasing the heat exchanger tube wall temperature above the flue gas acid dew point and water dew point. This prevents dust buildup and rapid corrosion of the heat pipes, extending the heat exchanger's service life. The specific working principle is as follows:

[0037] The heat exchanger's anti-ash-accumulation and corrosion structure includes an intermediate-temperature section ND steel bare tube heat exchanger assembly 1, a low-temperature section ND steel bare tube heat exchanger assembly 2, and a shock wave soot blower 3. The intermediate-temperature section bare tube heat exchanger assembly 1 operates within a flue gas temperature range of 150℃ to 290℃. Ammonium bisulfate in the flue gas is a viscous liquid in this temperature range; if it adheres to the heat exchanger tube wall, it will hydrolyze to release sulfuric acid and ammonia after boiler shutdown and subsequent moisture buildup. Therefore, the heat exchanger tubes are made of a bare tube structure that prevents ash accumulation and eliminates dead zones in the flue gas flow, and are made of ND steel resistant to sulfuric acid corrosion. At the top is a high-efficiency air-source shock wave soot blower 3, which utilizes the vibration and purging action of compressed air to clean the intermediate-temperature heat exchange section. The tube assembly undergoes periodic pulse cleaning to allow ammonium bisulfate mixed in the flue gas fly ash to be carried away by the flue gas, preventing accumulation and bridging between the heat exchange tubes. The low-temperature section ND steel bare tube heat exchange tube assembly 2 is located in a flue gas temperature of 120℃~150℃. Ammonium bisulfate in the flue gas is a solid crystal in this temperature range and can be carried away by the flue gas with the fly ash. When the tube wall temperature in the low-temperature section is low and the SO2 concentration in the flue gas is high, acid condensation is likely to form. The heat exchange tube material is a bare tube structure that is not easy to accumulate ash and ND steel that is resistant to sulfuric acid corrosion.

[0038] Boiler flue gas flows from top to bottom outside the heat exchanger tubes. The heat from the flue gas is transferred to the water flowing from bottom to top inside the heat exchanger tubes through convection. The water temperature increases along the direction of water flow, while the flue gas temperature decreases along the direction of flue gas flow.

[0039] A heat exchanger inlet water mixing and temperature control system 4 is installed at the front end of the heat exchanger inlet. It consists of a connecting pipe and a regulating valve between the boiler outlet water (90℃~130℃) main pipe and the heat exchanger inlet water pipe. It draws some boiler outlet water to mix and raise the heat exchanger inlet water temperature to above 65℃, thereby raising its pipe wall temperature to above the acid dew point (80℃), avoiding ash accumulation and rapid corrosion of the heat pipe, and extending the service life of the heat exchanger.

Claims

1. A device for preventing ash accumulation and corrosion in the waste heat recovery heat exchanger at the outlet of an industrial boiler SCR reactor, characterized in that, It includes a medium-temperature section ND steel bare tube heat exchanger assembly (1), a low-temperature section ND steel bare tube heat exchanger assembly (2), a shock wave soot blower (3), and a heat exchanger inlet water mixing and temperature control system (4). The medium-temperature section ND steel bare tube heat exchanger assembly (1) is set above the low-temperature section ND steel bare tube heat exchanger assembly (2). The shock wave soot blower (3) is located 300-450mm from the top row of tubes of the low-temperature section ND steel bare tube heat exchanger assembly (2) and is set before the water inlet of the low-temperature section ND steel bare tube heat exchanger assembly (2). The heat exchanger inlet water mixing and temperature control system (4) is connected to the inlet pipe of the low-temperature section ND steel bare tube heat exchanger tube group (2).

2. The anti-ash accumulation and corrosion device for the waste heat recovery heat exchanger at the outlet of the industrial boiler SCR reactor according to claim 1, characterized in that, The medium-temperature section ND steel bare tube heat exchanger assembly (1) and the low-temperature section ND steel bare tube heat exchanger assembly (2) are bare tube structures.

3. The anti-ash accumulation and corrosion device for the waste heat recovery heat exchanger at the outlet of the industrial boiler SCR reactor according to claim 1, characterized in that, The medium-temperature section ND steel bare tube heat exchanger tube assembly (1) is arranged in a serpentine pattern, and the low-temperature section ND steel bare tube heat exchanger tube assembly (2) is arranged in an S-shape.

4. The anti-ash accumulation and corrosion device for the waste heat recovery heat exchanger at the outlet of the industrial boiler SCR reactor according to claim 1, characterized in that, The medium-temperature section ND steel bare tube heat exchanger assembly (1) and the low-temperature section ND steel bare tube heat exchanger assembly (2) are directly connected through an intermediate header.

5. The anti-ash accumulation corrosion device for the waste heat recovery heat exchanger at the outlet of the industrial boiler SCR reactor according to claim 1, characterized in that, The heat exchanger inlet water mixing and temperature control system (4) draws a portion of hot water from the boiler outlet water pipe into the heat exchanger through a pipeline.

6. The anti-ash accumulation and corrosion device for the waste heat recovery heat exchanger at the outlet of the industrial boiler SCR reactor according to claim 5, characterized in that, The heat exchanger inlet water mixing and temperature control system (4) consists of the connecting pipes and regulating valves between the boiler outlet water header and the heat exchanger inlet water pipe.

Images