A low-temperature flash evaporation concentration device driven by flue gas waste heat

Abstract

The utility model discloses a low temperature flash evaporation concentration device of flue gas waste heat drive. Low temperature flash evaporation concentration device of flue gas waste heat drive, include: flue gas heat exchanger, intermediate heat exchanger, negative pressure flash evaporation tower, condenser and vacuum pump group, flue gas heat exchanger is equipped with flue gas import and flue gas export, is used for the import medium and low temperature flue gas, intermediate heat exchanger is connected with flue gas heat exchanger through circulation pipeline, forms intermediate medium circulation loop, is used for passing on flue gas heat to the raw liquid, the top of negative pressure flash evaporation tower is equipped with spray system, is equipped with demister in the upper part of tower, and the bottom part of tower is equipped with concentrated liquid export, the raw liquid export of intermediate heat exchanger is connected with spray system, the low temperature flash evaporation concentration device of flue gas waste heat drive provided by the utility model makes full use of medium and low temperature flue gas waste heat as core driving force, realizes efficient concentration under the condition of low temperature negative pressure, alleviates equipment scale problem significantly, reduces system energy consumption and investment cost simultaneously.

Description

Technical Field

[0001] This utility model relates to the field of industrial energy conservation and wastewater treatment technology, and in particular to a low-temperature flash evaporation and concentration device driven by flue gas waste heat. Background Technology

[0002] Existing industrial wastewater concentration or liquid material concentration technologies, such as multi-effect evaporation and mechanical vapor recompression, while mature, have significant shortcomings in utilizing the waste heat of medium- and low-temperature (typically 90-150℃) industrial flue gas. 1. High energy consumption: Although MVR technology is highly efficient, its core compressor requires a large amount of high-quality electrical energy, thus failing to truly achieve "waste treatment".

[0003] 2. Severe scaling and corrosion: The high temperature of the heat exchange wall of traditional evaporators easily leads to the rapid crystallization and adhesion of inorganic salts in the concentrate, forming hard scale, which seriously reduces heat transfer efficiency and requires frequent shutdowns for cleaning.

[0004] 3. Complex system and high investment: Whether it is multi-effect evaporation or MVR, the system contains a large number of pressure vessels, pumps and control systems, resulting in high initial investment and operation and maintenance costs.

[0005] 4. Insufficient utilization of waste heat: Waste heat from flue gas is often only used to preheat materials and is not used as the core driving force of the process, resulting in low energy utilization.

[0006] Therefore, it is necessary to provide a low-temperature flash evaporation and concentration device driven by flue gas waste heat to solve the above-mentioned technical problems. Utility Model Content

[0007] In response to the above situation and to overcome the shortcomings of the existing technology, this utility model provides a low-temperature flash evaporation and concentration device driven by flue gas waste heat. It can make full use of the waste heat of medium and low temperature flue gas as the core driving force, achieve efficient concentration under low temperature negative pressure conditions, and at the same time significantly alleviate the problem of equipment scaling, reduce system energy consumption and investment costs.

[0008] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A low-temperature flash evaporation and concentration unit driven by waste heat from flue gas includes: a flue gas heat exchanger, an intermediate heat exchanger, a negative pressure flash evaporation tower, a condenser, and a vacuum pump unit. The flue gas heat exchanger has a flue gas inlet and a flue gas outlet for introducing medium- and low-temperature flue gas. The intermediate heat exchanger is connected to the flue gas heat exchanger through a circulation pipeline to form an intermediate medium circulation loop for transferring heat from the flue gas to the raw liquid. The negative pressure flash evaporation tower has a spray system at the top, a demister at the upper part of the tower, and a concentrate outlet at the bottom. The raw liquid outlet of the intermediate heat exchanger is connected to the spray system. The secondary steam outlet of the negative pressure flash evaporation tower is connected to the steam inlet of the condenser. The vacuum pump unit is connected to the negative pressure flash evaporation tower through a suction pipeline to maintain the negative pressure of the system.

[0009] Preferably, the spray system is a centrifugal atomizer.

[0010] Preferably, an inverted conical flow guide shroud is provided below the centrifugal atomizer.

[0011] Preferably, a shallow conical liquid distribution tray is provided below the flow guide shroud.

[0012] Preferably, a stepped pressure-reducing liquid distributor is installed below the liquid distribution tray; the pressure-reducing liquid distributor includes a fixing ring that is sealed to the inner wall of the tower, and the fixing ring has a connection hole for fixing the exhaust pipe. Multiple perforated trays with gradually decreasing spacing are installed on the inner side of the fixing ring from top to bottom, and the connection hole is located between the two lowest perforated trays.

[0013] Preferably, the flue gas outlet of the flue gas heat exchanger is connected to a tail gas treatment device.

[0014] Preferably, the outlet of the concentrate of the negative pressure flash evaporator is connected to a concentrate pump via a pipeline, and the outlet of the concentrate pump is connected to a discharge pipeline and a return pipe to the negative pressure flash evaporator.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) By setting up a flue gas heat exchanger 2, an intermediate heat exchanger 3, a negative pressure flash evaporator 5, a condenser 6 and a vacuum pump group 7, this utility model can establish a negative pressure environment, significantly reduce the boiling point of the liquid, and make it match the temperature level of the waste heat of medium and low temperature flue gas, thereby achieving efficient and low-scaling flash evaporation concentration, reducing operating costs, solving the scaling problem of traditional evaporators, making full use of waste heat, and reducing carbon emissions and thermal pollution; (2) By setting up a tail gas treatment device 8 connected to the flue gas heat exchanger 2, this utility model can conveniently treat flue gas and is more environmentally friendly; (3) By installing a stepped pressure-reducing liquid distributor 15 below the liquid distribution tray 13, this utility model enables the liquid to flash multiple times, thereby improving the evaporation efficiency of the negative pressure flash evaporation tower 5. (4) This utility model can make full use of the waste heat of medium and low temperature flue gas as the core driving force to achieve efficient concentration under low temperature negative pressure conditions, while significantly alleviating the problem of equipment scaling and reducing system energy consumption and investment costs. Attached Figure Description

[0016] Figure 1 A schematic diagram of the low-temperature flash evaporation and concentration device driven by waste heat of flue gas provided by this utility model. Figure 2 This is a schematic diagram of the internal structure of a negative pressure flash evaporator; Figure 3 This is a schematic diagram of the pressure-reducing liquid distributor. Figure 4This is a cross-sectional view of the perforated tray.

[0017] The corresponding names of the attached figures are as follows: 1-Flue gas pipe, 2-Flue gas heat exchanger, 3-Intermediate heat exchanger, 4-Feed pipe, 5-Negative pressure flash tower, 6-Condenser, 7-Vacuum pump set, 8-Tail gas treatment device, 9-Spray system, 10-Liquid delivery pipe, 11-Demister, 12-Flow guide shroud, 13-Liquid distribution tray, 14-Extraction pipe, 15-Pressure reducing distributor, 16-Concentrate pump, 17-Return pipe, 18-Circulation pipe, 19-Fixing ring, 20-Perforated tray, 21-Connecting hole, 22-Small hole. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0019] Example 1: like Figure 1-4As shown, the low-temperature flash evaporation and concentration device driven by waste heat of flue gas provided by this utility model includes: a flue gas heat exchanger 2, an intermediate heat exchanger 3, a negative pressure flash evaporation tower 5, a condenser 6, and a vacuum pump group 7; medium- and low-temperature flue gas enters the flue gas heat exchanger 2 through the flue gas pipe 1, and is then discharged after cooling. The flue gas heat exchanger 2 and the intermediate heat exchanger 3 exchange heat through a circulation pipe 18. The intermediate medium is pumped and circulates between the flue gas heat exchanger 2 and the intermediate heat exchanger 3 along the route of the circulation pipe 18. The heat of the flue gas in the flue gas heat exchanger 2 is transferred... An intermediate medium is supplied, raising its temperature. The ambient temperature raw liquid enters the intermediate heat exchanger 3 through the feed pipe 4, where it exchanges heat with the intermediate medium and is preheated to a temperature close to the boiling point of the negative pressure flash evaporator 5 (e.g., 58°C). The preheated raw liquid (appropriately pressurized) is then sent to the spray system 9 within the negative pressure flash evaporator 5 through the delivery pipe 10. The raw liquid is sprayed into the negative pressure flash evaporator 5 through nozzles on the spray system 9, where it is atomized into tiny droplets. Due to the large specific surface area of ​​the droplets and the fact that the ambient pressure is lower than the saturation pressure corresponding to their current temperature, the droplets instantly and violently boil (flash evaporation), and the water evaporates rapidly. The resulting water vapor rises within the tower, carrying droplets that are captured and separated in the demister 11 at the top of the tower. The dried secondary steam enters the condenser 6. The steam is condensed by cooling water in the condenser, and the released latent heat can be used to preheat the feed raw liquid or for other purposes. The condensate is recovered. Non-condensable gases are extracted by vacuum pump unit 7 to maintain negative pressure in the system. After flash evaporation, the concentrated and cooled droplets fall to the bottom of the tower and are discharged by concentrate pump 16, achieving the preset concentration ratio. Part of the concentrate can be circulated back into the tower through return pipe 17 to control the discharge concentration and reduce scaling. The unit utilizes the previously unusable waste heat from medium- and low-temperature flue gas as the sole process-driven energy source, achieving true energy cascade utilization and "zero" external energy concentration. The core concentration process is carried out at a low temperature of 45-65℃, significantly slowing the crystallization rate of inorganic salts such as CaSO4 and CaCO3, making it less likely to form hard, dense scale. Spray flash evaporation is used, with evaporation occurring on the droplet surface, avoiding scale formation on high-temperature heat exchange walls and solving the most troublesome scaling problem of traditional evaporators. Expensive steam boilers or high-power compressors are eliminated. The main energy-consuming equipment consists only of vacuum pumps, circulating working fluid pumps, and material pumps, all of which are low-power devices, significantly reducing operating costs. The atomized droplets create a huge gas-liquid contact area, making the flash evaporation process very rapid and efficient, with a large processing capacity per unit volume of equipment. It also makes full use of waste heat, reducing carbon emissions and thermal pollution throughout the plant.

[0020] By setting up a flue gas heat exchanger 2, an intermediate heat exchanger 3, a negative pressure flash evaporator 5, a condenser 6, and a vacuum pump group 7, a negative pressure environment can be established, significantly reducing the boiling point of the liquid and matching it with the temperature level of the waste heat from the medium and low temperature flue gas. This enables efficient and low-fouling flash concentration, reduces operating costs, solves the scaling problem of traditional evaporators, makes full use of waste heat, and reduces carbon emissions and thermal pollution.

[0021] Example 2: like Figure 1 As shown, an extraction pipe 14 is installed between the vacuum pump group 7 and the negative pressure flash evaporator 5. The extraction pipe 14 facilitates the extraction of gas from the tower by the vacuum pump group 7, resulting in negative pressure inside the negative pressure flash evaporator 5 and a decrease in the boiling point of the liquid.

[0022] By installing an extraction pipe 14 between the vacuum pump group 7 and the negative pressure flash tower 5, the gas inside the negative pressure flash tower 5 can be extracted.

[0023] Example 3: like Figure 1 As shown, a tail gas treatment device 8 is installed on the flue gas heat exchanger 2 via a pipe. The tail gas treatment device 8 performs subsequent treatment on the cooled flue gas so that it can meet the emission standards.

[0024] By installing a tail gas treatment device 8 connected to the flue gas heat exchanger 2, the flue gas can be treated conveniently, making it more environmentally friendly.

[0025] Example 4: like Figure 2 As shown, in this embodiment, the spray system 9 is a centrifugal atomizer. Compared to ordinary nozzles, the centrifugal atomizer uses a high-speed rotating disc or wheel to pull the liquid into a thin film and break it into more uniform and finer droplets. This not only greatly increases the mass transfer area, but also fundamentally eliminates the clogging problem due to the absence of small-aperture channels, making it particularly suitable for processing concentrated liquids with a tendency to precipitate and crystallize.

[0026] Furthermore, an inverted conical flow guide shroud 12 is installed below the centrifugal atomizer to ensure that the atomized droplets flow downwards evenly, preventing droplets from drifting towards the tower wall and reducing scaling on the wall surface. The flow guide shroud 12 is fixed inside the tower by welding or other methods.

[0027] Furthermore, a shallow conical liquid distribution tray 13 is installed below the flow guide shroud 12. The center of the liquid distribution tray 13 is slightly lower. This tray collects incompletely evaporated droplets and redistributes them to form a thin liquid film. The liquid film flows downward under gravity while continuing to flash under negative pressure. The conical design ensures that the liquid flows rapidly to the center without stagnation. At the same time, a portion of the concentrate from the bottom of the column is pumped to the liquid distribution tray 13 for high-flow-rate circulation via the concentrate pump 16 and the return pipe 17. This allows the tray to be flushed with a relatively low-concentration circulating liquid, preventing supersaturation and crystallization due to liquid retention, while also providing a second opportunity for concentrated flash evaporation of the material.

[0028] The above structural design further optimizes the evaporation process of the liquid in the negative pressure flash evaporator 5.

[0029] Example 5: like Figure 2-4 As shown, a stepped pressure-reducing liquid distributor 15 is installed below the liquid distribution tray 13 inside the negative pressure flash evaporator 5. The pressure-reducing liquid distributor 15 includes a fixing ring 19 with a connection hole 21. The outer edge of the fixing ring 19 is sealed to the inner wall of the tower, and the exhaust pipe 14 is inserted into the connection hole 21 for sealing and fixation. Multiple perforated trays 20 are installed inside the fixing ring 19, and the spacing gradually decreases from top to bottom. The connection hole 21 is located between the two lowest perforated trays 20, so that when liquid falls from the upper perforated tray 20 through the small hole 22... When the flow channel suddenly narrows, the flow velocity increases. According to Bernoulli's principle, at the instant the flow velocity increases (like a cascading liquid column or jet), the local static pressure of the liquid will be lower than the average pressure of the gas phase space in the lower tray. The liquid flashes as it passes through this lower-pressure "jet zone". When the liquid falls to the next tray, the pressure recovers. However, due to the position of the evacuation pipe 4, the pressure in the gas phase space corresponding to the multiple perforated trays 20 decreases step by step from top to bottom, thus achieving a "step-like" pressure drop and multiple flashes.

[0030] By installing a stepped pressure-reducing liquid distributor 15 below the liquid distribution tray 13, the liquid can be flashed multiple times, thereby improving the evaporation efficiency of the negative pressure flash evaporation tower 5.

[0031] Working principle: During operation, medium- and low-temperature flue gas enters the flue gas heat exchanger 2 through the flue gas pipe 1, and is then discharged after cooling. The flue gas heat exchanger 2 and the intermediate heat exchanger 3 exchange heat through the circulation pipe 18. The intermediate medium is pumped along the route of the circulation pipe 18 and circulates between the flue gas heat exchanger 2 and the intermediate heat exchanger 3. The heat of the flue gas in the flue gas heat exchanger 2 is transferred to the intermediate medium, causing the temperature of the intermediate medium to rise. The room temperature raw liquid enters the intermediate heat exchanger 3 through the feed pipe 4 and exchanges heat with the intermediate medium. It is preheated to a temperature close to the boiling point of the negative pressure flash tower 5. The preheated raw liquid is sent to the spray system 9 in the negative pressure flash tower 5 through the liquid delivery pipe 10. The raw liquid is sprayed into the negative pressure flash tower 5 through the nozzles on the spray system 9 and atomized into tiny droplets in the negative pressure flash tower 5. Due to the large specific surface area of ​​the droplets and the fact that the ambient pressure is lower than the saturation pressure corresponding to their current temperature, the droplets undergo instantaneous and violent boiling (flash evaporation), causing rapid evaporation of water. The resulting water vapor rises within the column, carrying droplets that are captured and separated in the demister 11 at the top of the column. The dried secondary steam enters the condenser 6. The steam is condensed by cooling water in the condenser 6, and the released latent heat can be used to preheat the feed liquid or for other purposes. The condensate is recovered. Non-condensable gases are extracted by the vacuum pump unit 7 to maintain the negative pressure of the system. The droplets, with increased concentration and decreased temperature after flash evaporation, fall to the bottom of the column and are discharged by the concentrate pump 16, achieving the preset concentration ratio. A portion of the concentrate can be circulated back into the column through the return pipe 17 to control the discharge concentration and reduce scaling.

Claims

1. A low-temperature flash evaporation and concentration device driven by waste heat from flue gas, characterized in that, include: Flue gas heat exchanger (2), intermediate heat exchanger (3), negative pressure flash tower (5), condenser (6) and vacuum pump group (7); The flue gas heat exchanger (2) is provided with a flue gas inlet and a flue gas outlet; The intermediate heat exchanger (3) is connected to the flue gas heat exchanger (2) through a circulation pipeline (18); The negative pressure flash evaporator (5) is equipped with a spray system (9) at the top and a demister (11) is installed in the negative pressure flash evaporator (5). The intermediate heat exchanger (3) is connected to the spray system (9); The secondary steam outlet of the negative pressure flash evaporator (5) is connected to the steam inlet of the condenser (6); The vacuum pump unit (7) is connected to the negative pressure flash tower (5) through the air extraction pipeline (14) to maintain the negative pressure of the system.

2. The low-temperature flash evaporation and concentration device driven by waste heat of flue gas according to claim 1, characterized in that, The spray system (9) is a centrifugal atomizer.

3. The low-temperature flash evaporation and concentration device driven by flue gas waste heat according to claim 2, characterized in that, The centrifugal atomizer is provided with an inverted conical flow guide shroud (12) below it.

4. The low-temperature flash evaporation and concentration device driven by flue gas waste heat according to claim 3, characterized in that, A shallow conical liquid distribution tray (13) is provided below the flow guide shroud (12).

5. A low-temperature flash evaporation and concentration device driven by waste heat of flue gas according to claim 4, characterized in that, A stepped pressure-reducing liquid distributor (15) is installed below the liquid distribution tray (13). The pressure reducing liquid distributor (15) includes a fixing ring (19) that is sealed to the inner wall of the tower. The fixing ring (19) has a connection hole (21) for fixing the gas extraction pipeline (14). Multiple perforated trays (20) with gradually decreasing spacing are installed on the inner side of the fixing ring (19) from top to bottom. The connection hole (21) is located between the two lowest perforated trays (20).

6. A low-temperature flash evaporation and concentration device driven by waste heat of flue gas according to any one of claims 1 to 5, characterized in that, The flue gas outlet of the flue gas heat exchanger (2) is connected to a tail gas treatment device (8).

7. A low-temperature flash evaporation and concentration device driven by waste heat of flue gas according to any one of claims 1 to 5, characterized in that, The concentrated liquid outlet of the negative pressure flash evaporator (5) is connected to a concentrated liquid pump (16) via a pipeline. The outlet of the concentrated liquid pump (16) is connected to a discharge pipeline and a return pipe (17) to the negative pressure flash evaporator (5).

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