Desulfurization wastewater low-temperature evaporation device with enhanced heat transfer and film-forming properties

Abstract

The utility model discloses a desulfurized wastewater low-temperature evaporation device capable of enhancing heat transfer and film-forming properties, which is based on a dividing wall type heat exchange and air moisture-carrying gas-liquid phase balance principle, utilizes ultralow-temperature waste heat of clean flue gas in a desulfurizing tower to heat circulating hot fluid, and is characterized in that finned tube bundles and light tube bundles in a low-temperature evaporation tower are arranged in a combined manner; air and spraying water are used for cooling circulating hot fluid in the tube bundle, the air provides a power source at the same time, evaporation and concentration of desulfurization waste water are achieved, the low-temperature evaporation system does not need to additionally consume a heat source, ultralow-temperature waste heat of clean flue gas can be utilized, heat transfer is enhanced, the scaling risk is reduced, and the energy-saving performance and stability of the low-temperature evaporation system are improved on the whole.

Description

Technical Field

[0001] This utility model belongs to the field of desulfurization wastewater technology, and in particular relates to a low-temperature evaporation device for desulfurization wastewater that enhances heat transfer and film formation performance. Background Technology

[0002] In limestone-gypsum wet flue gas desulfurization (FGD) systems of large thermal power plants, some FGD wastewater needs to be discharged to ensure desulfurization efficiency and maintain system chloride ion balance. Traditional FGD wastewater treatment processes mainly employ physicochemical methods, which are complex, discharge high-salinity wastewater, require numerous equipment units, and incur high operating and maintenance costs. With the increasing emphasis on environmental protection by the state, the goal of achieving zero discharge of FGD wastewater is becoming increasingly important, posing a serious challenge to the sustainable development of the coal-fired boiler sector.

[0003] From the perspective of the economy and energy consumption of zero discharge of desulfurization wastewater, the concentration and volume reduction stage is crucial, with electricity and steam consumption in the concentration stage accounting for more than 60% of the operating cost per ton of wastewater treated. Concentration and volume reduction are mainly divided into two categories: membrane concentration and thermal concentration. Membrane concentration has strict requirements on the quality of influent water and is prone to scaling and clogging, which limits its large-scale industrial application. Thermal concentration can utilize the waste heat of high and low grade flue gas to evaporate the water in desulfurization wastewater, becoming the mainstream technology in the field of zero wastewater discharge. Among them, the main flue evaporation technology and the bypass flue evaporation technology are more commonly used in thermal power plants. However, the main flue evaporation technology has a small wastewater treatment capacity, is greatly affected by boiler load, is not suitable for power plants with flue gas coolers installed before the dust collector, and is prone to problems such as pipeline corrosion, dust collector agglomeration, and excessively low flue gas emission temperature. The bypass flue evaporation technology can avoid these problems. Whether it's the main flue gas evaporation technology or the bypass flue gas evaporation technology, the heat source is the waste heat of the flue gas in front of the desulfurization tower. It is rare to utilize the ultra-low temperature waste heat of the clean flue gas inside the desulfurization tower. Moreover, desulfurization wastewater with high salt content and high corrosiveness is prone to scaling and clogging during the evaporation and concentration process, which affects the stable operation of the system.

[0004] This invention provides a low-temperature evaporation device for desulfurization wastewater that enhances heat transfer and film formation performance. Based on the principle of indirect heat exchange and air-carrying humidified liquid-phase equilibrium, it utilizes the ultra-low temperature waste heat of the clean flue gas in the desulfurization tower to heat the circulating hot fluid. The finned tube bundle and the bare tube bundle are arranged in combination in the low-temperature evaporation tower. Air and spray water are used to cool the circulating hot fluid in the tube bundle. The air also provides a power source to achieve the evaporation and concentration of desulfurization wastewater. This invention has the advantages of not requiring additional heat sources and utilizing the ultra-low temperature waste heat of clean flue gas, enhancing heat transfer and reducing the risk of scaling, thus improving the energy efficiency and stability of the low-temperature evaporation system as a whole. Summary of the Invention

[0005] The purpose of this invention is to provide a low-temperature evaporation device for desulfurized wastewater that enhances heat transfer and film formation performance. It utilizes the ultra-low temperature waste heat of the clean flue gas in the desulfurization tower to achieve evaporation and concentration of desulfurized wastewater, thereby enhancing heat transfer and reducing the risk of scaling. Overall, it improves the energy efficiency and stability of the low-temperature evaporation system.

[0006] To solve the above problems, the present invention adopts the following technical solution: a low-temperature evaporation device for desulfurization wastewater that enhances heat transfer and film formation performance, comprising a low-temperature evaporation tower, a bare tube bundle, a finned tube bundle, a spray device, a demisting device, a desulfurization wastewater concentration tank, a desulfurization wastewater circulation pump, an air inlet, a finned tube bundle inlet, a finned tube bundle outlet, a bare tube bundle inlet, a bare tube bundle outlet, a flow equalization device, a desulfurization wastewater discharge outlet, a water-facing surface, a water-returning surface, and fins. The finned tube bundle and the bare tube bundle are arranged in combination inside the low-temperature evaporation tower. The circulating heat fluid enters the low-temperature evaporation tower from the finned tube bundle inlet after absorbing the ultra-low temperature waste heat of the clean flue gas in the desulfurization tower for heat exchange. The finned tube bundle outlet is connected to the bare tube bundle inlet. After the circulating heat fluid is cooled in the low-temperature evaporation tower, it flows out from the bare tube bundle outlet and enters the desulfurization tower to absorb the ultra-low temperature waste heat of the clean flue gas in the desulfurization tower.

[0007] The demister is positioned above the spray system, which is located between the demister and the finned tube bundle. The finned tube bundle is positioned between the spray system and the bare tube bundle. The bare tube bundle is positioned between the finned tube bundle and the flow equalization device. The flow equalization device is positioned between the bare tube bundle and the air inlet. The air inlet is positioned between the flow equalization device and the desulfurization wastewater concentration tank. The desulfurization wastewater concentration tank is located at the bottom of the low-temperature evaporator, which is located near the desulfurization tower. The finned tube bundle has a maximum of two rows of tubes, with fins arranged in a semi-circular pattern and only on the water-facing side. There are no fins on the back side. The flow equalization device is a guide plate with inclined holes.

[0008] The spraying device atomizes the desulfurization wastewater drawn from the desulfurization wastewater thickening tank into small droplets at a certain pressure and sprays them downwards. The desulfurization wastewater first comes into direct heat transfer with the upward-flowing air in a counter-current contact. Smaller droplets vaporize directly during the counter-current contact with the air, while larger droplets impact the surface of the finned tube bundle and exchange heat with the circulating hot fluid inside the finned tube bundle. Then, it passes through the bare tube bundle and exchanges heat with the circulating hot fluid inside the bare tube bundle. While the sprayed desulfurization wastewater is undergoing indirect heat exchange, it also comes into counter-current contact with the rising air and exchanges heat and mass. Then, it enters the desulfurization wastewater thickening tank. The concentrated desulfurization wastewater enters the flue gas evaporation or other zero-discharge devices through the desulfurization wastewater discharge port.

[0009] The circulating heat fluid absorbs heat outside the low-temperature evaporation tower and releases heat inside the low-temperature evaporation tower. The heat source for heating the circulating heat fluid is the ultra-low temperature waste heat of the clean flue gas in the desulfurization tower. No additional heat source is required, and the deep utilization of the low-grade heat source is achieved. The air is at room temperature. The air and the sprayed desulfurization wastewater cool the circulating heat fluid in the tube bundle, and the air also provides a power source.

[0010] After being sprayed, the desulfurization wastewater directly impacts the water-facing surface of the finned tube bundle. However, the number of rows of tubes that can be impacted is limited. Generally, only the top two rows of tube bundles can be impacted. The outer boundary layer of the impacted finned tube bundle is very thin, and its heat transfer coefficient is several times or even an order of magnitude higher than that of ordinary in-tube heat exchange. Due to the obstruction of the fins, the reflection of the desulfurization wastewater after impacting the finned tube bundle is reduced, the coverage of the desulfurization wastewater on the finned tube bundle is increased, the effective impact area is increased, the heat transfer area is increased, and the heat transfer is enhanced.

[0011] Although finned tube bundles increase the heat transfer area, their surface cannot be completely wetted, the surface water has poor film-forming properties, the amount of water evaporating on the finned tube bundle is very small, the water evaporation efficiency is very low, and water and scale easily accumulate at the root of the fins, which is difficult to clean, increasing the thermal resistance. The heat load removed by the evaporation of water on the finned tube bundle is limited, generally less than 30% of the total load. Most of the heat load inside the tubes is mainly removed by the temperature rise of the air after humidification and cooling.

[0012] As the desulfurization wastewater flows downwards, the moisture in the wastewater migrates into the air, increasing its concentration and making it prone to scaling on the finned tube bundles. A maximum of two rows of finned tube bundles are arranged, with bare tube bundles positioned below them. When the desulfurization wastewater impacts the water-facing surface of the bare tube bundles, the good film-forming properties of the tube surface allow for continued turbulence along the circumference, forming a vortex zone on the back surface. Since there is no fin obstruction on the back surface, the vortex zone develops both axially and circumferentially on the heat exchange tubes, preventing scaling on the back surface. The combined arrangement of finned and bare tube bundles in the low-temperature evaporator tower improves the heat transfer coefficient and avoids scaling on the heat exchange surface after the desulfurization wastewater concentration increases.

[0013] Compared with the prior art, the present invention discloses a low-temperature evaporation device for desulfurization wastewater that enhances heat transfer and film formation performance. It utilizes the ultra-low temperature waste heat of the clean flue gas in the desulfurization tower to achieve evaporation and concentration of desulfurization wastewater, enhances heat transfer and reduces the risk of scaling, and improves the energy efficiency and stability of the low-temperature evaporation system as a whole. Attached Figure Description

[0014] The invention will now be described in more detail with the aid of the accompanying drawings, in which the same reference numerals denote the same elements.

[0015] Figure 1 This is a schematic diagram showing the overall layout of a low-temperature evaporation device for desulfurization wastewater that enhances heat transfer and film formation performance.

[0016] Figure 2 This is a cross-sectional view of a single tube in a finned tube bundle of a low-temperature evaporation device for desulfurized wastewater that enhances heat transfer and film formation performance.

[0017] In the above figures, 1 is a low-temperature evaporation tower, 2 is a bare tube bundle, 3 is a finned tube bundle, 4 is a spray device, 5 is a demister, 6 is a desulfurization wastewater concentration tank, 7 is a desulfurization wastewater circulation pump, 8 is an air inlet, 9 is a finned tube bundle inlet, 10 is a finned tube bundle outlet, 11 is a bare tube bundle inlet, 12 is a bare tube bundle outlet, 13 is a flow equalization device, 14 is a desulfurization wastewater discharge outlet, 15 is the water-facing surface, 16 is the water-returning surface, and 17 is a fin. Detailed Implementation

[0018] The embodiments of this utility model will now be described in detail with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features described herein can be combined with each other. It should be noted that those skilled in the art can make modifications or alterations to this utility model without departing from its principles, and such modifications or alterations also fall within the protection scope of the claims of this utility model.

[0019] like Figure 1 As shown, a low-temperature evaporation device for desulfurization wastewater with enhanced heat transfer and film formation performance includes a low-temperature evaporation tower, a bare tube bundle, a finned tube bundle, a spray device, a demister, a desulfurization wastewater concentration tank, a desulfurization wastewater circulation pump, an air inlet, a finned tube bundle inlet, a finned tube bundle outlet, a bare tube bundle inlet, a bare tube bundle outlet, a flow equalization device, a desulfurization wastewater discharge outlet, a water-facing surface, a water-returning surface, and fins. The finned tube bundle and the bare tube bundle are arranged in combination inside the low-temperature evaporation tower. The circulating heat fluid enters the low-temperature evaporation tower from the finned tube bundle inlet after absorbing the ultra-low temperature waste heat of the clean flue gas in the desulfurization tower for heat exchange. The finned tube bundle outlet is connected to the bare tube bundle inlet. After the circulating heat fluid is cooled in the low-temperature evaporation tower, it flows out from the bare tube bundle outlet and enters the desulfurization tower to absorb the ultra-low temperature waste heat of the clean flue gas in the desulfurization tower.

[0020] The demister is positioned above the spray system, which is located between the demister and the finned tube bundle. The finned tube bundle is positioned between the spray system and the bare tube bundle. The bare tube bundle is positioned between the finned tube bundle and the flow equalization device. The flow equalization device is positioned between the bare tube bundle and the air inlet. The air inlet is positioned between the flow equalization device and the desulfurization wastewater concentration tank. The desulfurization wastewater concentration tank is located at the bottom of the low-temperature evaporator, which is located near the desulfurization tower. The finned tube bundle has a maximum of two rows of tubes, with fins arranged in a semi-circular pattern and only on the water-facing side. There are no fins on the back side. The flow equalization device is a guide plate with inclined holes.

[0021] The spraying device atomizes the desulfurization wastewater drawn from the desulfurization wastewater thickening tank into small droplets at a certain pressure and sprays them downwards. The desulfurization wastewater first comes into direct heat transfer with the upward-flowing air in a counter-current contact. Smaller droplets vaporize directly during the counter-current contact with the air, while larger droplets impact the surface of the finned tube bundle and exchange heat with the circulating hot fluid inside the finned tube bundle. Then, it passes through the bare tube bundle and exchanges heat with the circulating hot fluid inside the bare tube bundle. While the sprayed desulfurization wastewater is undergoing indirect heat exchange, it also comes into counter-current contact with the rising air and exchanges heat and mass. Then, it enters the desulfurization wastewater thickening tank. The concentrated desulfurization wastewater enters the flue gas evaporation or other zero-discharge devices through the desulfurization wastewater discharge port.

[0022] like Figure 2 As shown, the finned tube bundle of a desulfurization wastewater low-temperature evaporation device with enhanced heat transfer and film formation performance has fins arranged in a semi-circular manner and only on the water-facing side, with no fins on the back side.

[0023] The above describes typical embodiments of the present invention, but the present invention is not limited to the above embodiments, and various modifications or changes can be made within the scope of the claims.

Claims

1. A low-temperature evaporation device for desulfurization wastewater with enhanced heat transfer and film formation properties, characterized in that, The invention includes a low-temperature evaporation device for desulfurization wastewater that enhances heat transfer and film formation performance. The device comprises a low-temperature evaporation tower, a bare tube bundle, a finned tube bundle, a spray device, a demister, a desulfurization wastewater concentration tank, a desulfurization wastewater circulation pump, an air inlet, a finned tube bundle inlet, a finned tube bundle outlet, a bare tube bundle inlet, a bare tube bundle outlet, a flow equalization device, a desulfurization wastewater discharge outlet, a water-facing surface, a water-returning surface, and fins. The finned tube bundle and bare tube bundle are arranged in combination within the low-temperature evaporation tower. The circulating heat fluid, after absorbing the ultra-low temperature waste heat from the clean flue gas in the desulfurization tower, enters the low-temperature evaporation tower from the finned tube bundle inlet for heat exchange. The finned tube bundle outlet is connected to the bare tube bundle inlet. After cooling within the low-temperature evaporation tower, the circulating heat fluid flows out from the bare tube bundle outlet and enters the desulfurization tower to absorb the ultra-low temperature waste heat from the clean flue gas in the desulfurization tower.

2. The low-temperature evaporation device for desulfurization wastewater with enhanced heat transfer and film formation properties according to claim 1, characterized in that, The demister is positioned above the spray device, the spray device is positioned between the demister and the finned tube bundle, the finned tube bundle is positioned between the spray device and the bare tube bundle, the bare tube bundle is positioned between the finned tube bundle and the flow equalization device, the flow equalization device is positioned between the bare tube bundle and the air inlet, the air inlet is positioned between the flow equalization device and the desulfurization wastewater concentration tank, the desulfurization wastewater concentration tank is located at the bottom of the low-temperature evaporation tower, and the low-temperature evaporation tower is located near the desulfurization tower.

3. The low-temperature evaporation device for desulfurization wastewater with enhanced heat transfer and film formation properties according to claim 1, characterized in that, The finned tubes have a maximum of two rows, and the finned tube bundles are arranged above the smooth tube bundles. The smooth tubes have a minimum of one row.

4. The low-temperature evaporation device for desulfurization wastewater with enhanced heat transfer and film formation properties according to claim 1, characterized in that, The finned tube bundle has fins arranged in a semi-circular pattern and only on the water-facing side, with no fins on the water-repellent side.

5. The low-temperature evaporation device for desulfurization wastewater with enhanced heat transfer and film formation properties according to claim 1, characterized in that, The flow equalization device is a guide inclined plate.

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