Solar salt-containing wastewater evaporation system based on dry-wet composite channel

Abstract

The present application belongs to the technical field of salt wastewater evaporation treatment, and particularly relates to a solar salt-containing wastewater evaporation system based on dry-wet composite channels, which comprises a feed liquid tank, a regenerator and a dry-wet composite channel humidifier, the dry-wet composite channel humidifier comprises a plurality of composite channels, each of which comprises a dry channel and a wet channel, and a partition plate is arranged between the dry channel and the wet channel, and the partition plate is provided with a plurality of communication holes; the dry-wet composite channel humidifier is used to replace the conventional evaporator, the dry-wet composite channel is composed of the dry channel and the wet channel, the heat and mass transfer in the dew point evaporation process is balanced through the synergistic effect of the indirect heat exchange of the dry channel and the direct heat and mass transfer of the wet channel, the air temperature and enthalpy operating line in the dew point evaporation process is far away from the saturation curve, the heat and mass transfer difference in the dew point evaporation process is reduced, thereby the entropy increase is reduced, at the same time, the wet air temperature and enthalpy operating line in the regenerator tends to be a straight line, thereby the system entropy increase is further reduced, and the system thermal efficiency is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of salt wastewater evaporation treatment, and particularly relates to a solar salt-containing wastewater evaporation system based on a dry-wet composite channel. BACKGROUND

[0002] Evaporation concentration is the core unit of the high-salt wastewater treatment process, and is a high-cost and high-energy-consumption process. Traditional energy-saving evaporation technologies such as mechanical vapor recompression and multi-effect evaporation are mainly driven by fossil fuels, which have high energy consumption and large carbon emissions, and it is difficult to achieve low-carbon evaporation of high-salt wastewater. Therefore, there is an urgent need to seek a new evaporation technology to achieve low-carbon evaporation treatment of salt-containing wastewater.

[0003] The dew point evaporation technology is a new evaporation technology, which realizes evaporation and water production by simulating rainwater circulation and using air humidification and dehumidification process. The dew point evaporation technology can realize atmospheric low-temperature evaporation, has low requirements for heat source quality, can efficiently utilize low-grade waste heat and renewable energy such as solar energy and geothermal energy, and can use low-cost corrosion-resistant materials such as polypropylene, thereby reducing manufacturing and maintenance costs. However, compared with multi-effect evaporation and mechanical vapor recompression technology, the conventional dew point evaporation technology has relatively low efficiency, and improving the efficiency of the dew point evaporation technology is the key to further popularization and application of the technology. SUMMARY

[0004] The technical problem to be solved by the application is to solve the problems of high energy consumption, large carbon emissions and difficulty in achieving low-carbon evaporation of high-salt wastewater in the prior art, and to provide a solar salt-containing wastewater evaporation system based on a dry-wet composite channel.

[0005] The technical solution adopted by the application to solve the technical problem is a solar salt-containing wastewater evaporation system based on a dry-wet composite channel, comprising:

[0006] A feed liquid tank for storing brine;

[0007] A regenerator for heating wet air and brine from the feed liquid tank;

[0008] And a dry-wet composite channel humidifier comprising a shell having an inner cavity, the shell being provided at the upper end with a high-temperature liquid inlet for connecting the inner cavity with a high-temperature liquid outlet of the regenerator and a high-temperature gas inlet for connecting the inner cavity with a high-temperature gas outlet of the regenerator, and at the lower end with an air inlet and a liquid outlet connected with the inner cavity;

[0009] The inner cavity is provided with a plurality of composite channels arranged side by side and having an open lower end for air to enter, and each composite channel comprises a dry channel blocked at the upper end and a wet channel open at the upper end for liquid to flow in, and a longitudinal porous partition plate is arranged between the dry channel and the wet channel, the longitudinal porous partition plate is provided with a plurality of communication holes for connecting the dry channel and the wet channel along the longitudinal direction.

[0010] Further, a solar heat collector is arranged between the high-temperature outlet of the regenerator and the high-temperature inlet of the dry-wet composite channel humidifier for heating the brine flowing out of the high-temperature outlet of the regenerator.

[0011] Further, a spraying device is arranged above the composite channel and communicates with the high-temperature inlet for spraying the brine.

[0012] Further, a demister is arranged above the spraying device for removing the liquid droplets carried in the air.

[0013] Further, the regenerator has a low-temperature outlet for discharging the condensed water formed after the air is exchanged, and the low-temperature outlet is connected with a condensed water tank.

[0014] Further, the regenerator has a low-temperature outlet for discharging the condensed water formed after the air is exchanged, and the low-temperature outlet is connected with a condensed water tank.

[0015] Further, the air inlet of the dry-wet composite channel humidifier is connected with an air inlet pipe, and a fan is arranged on the air inlet pipe, and a fan inlet of the fan communicates with the atmosphere and / or a gas outlet of the gas-liquid separation tank.

[0016] Further, a first valve is arranged on the pipeline between the fan inlet and the atmosphere, and a second valve is arranged between the fan inlet and the outlet of the gas-liquid separation tank.

[0017] Further, the liquid tank communicates with the liquid discharge outlet of the dry-wet composite channel humidifier, and a third valve is arranged therebetween.

[0018] Further, a liquid pump is arranged between the liquid tank and the regenerator for conveying the brine in the liquid tank to the regenerator, and a concentrated brine pump is arranged on the liquid discharge outlet of the dry-wet composite channel humidifier.

[0019] The present application has the following advantages:

[0020] 1. The dry-wet composite channel humidifier is used to replace the conventional evaporator, the dry-wet composite channel is composed of a dry channel and a wet channel, the heat and mass transfer in the dew point evaporation process is balanced through the synergistic effect of the indirect heat exchange in the dry channel and the direct heat and mass transfer in the wet channel, the air temperature and enthalpy operating line in the dew point evaporation process is far away from the saturation curve, the heat and mass transfer difference in the dew point evaporation process is reduced, the entropy increase in the humidification process is reduced, the temperature and enthalpy operating line of the wet air in the regenerator tends to be a straight line, the system entropy increase is further reduced, and the system thermal efficiency is improved.

[0021] 2. Air adopts semi-closed cycle, part of the wet air at the outlet of the regenerator is returned to the system, mixed with fresh air from outside, and then re-enters the system cycle. The air return can recover part of the waste heat in the wet air, avoiding direct discharge from the system to cause heat waste, and improving the thermal efficiency of the system. The use of fresh air circulation can improve the evaporation efficiency of the system, because the fresh air has lower temperature and humidity, and can absorb more water in the humidifier. Through semi-closed air circulation, the proportion of fresh air and return air can be adjusted to balance the thermal efficiency and evaporation efficiency, and can be adjusted according to the actual operation requirements of the system.

[0022] 3. The required heat source temperature of the system is low, so the required heat can be provided by renewable energy such as solar energy and geothermal energy, thereby reducing the consumption of fossil energy.

[0023] Other features of the present application and its advantages will become apparent from the following detailed description of exemplary embodiments thereof, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0024] The application will be further described below with reference to the accompanying drawings and examples.

[0025] Figure 1 Figure 1 is a process flow diagram of a solar salt-containing wastewater evaporation system based on dry-wet composite channels;

[0026] Figure 2 Figure 2 is a schematic diagram of a dry-wet composite channel structure;

[0027] Figure 3 Figure 3 is a temperature-enthalpy operating line of a dry-wet composite channel evaporation system;

[0028] Figure 4 Figure 4 is a comparison curve of thermal efficiency between a conventional system and an evaporation system based on a wet composite channel.

[0029] In the figure:

[0030] 1. Feed liquid tank; 2. Feed liquid pump; 3. Regenerator; 4. Solar collector; 5. Dry-wet composite channel humidifier; 501. Shell; 502. Composite channel; 5021. Dry channel; 5022. Wet channel; 5023. Partition; 5024. Baffle; 503. Spraying device; 504. Demister; 6. Concentrated brine pump; 7. Fan; 8. Gas-liquid separation tank; 9. Condensate tank; 10. First valve; 11. Second valve; 12. Third valve. DETAILED DESCRIPTION

[0031] The application will now be described in further detail with reference to the drawings. These drawings are simplified schematic illustrations of the basic structure of the application, and are therefore only showing the features relevant to the application, and the directions and references (e.g. up, down, left, right, etc.) can only be used to facilitate the description of the features in the drawings. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the subject matter sought to be protected is defined only by the claims that follow and equivalents thereof.

[0032] As shown in the drawings, a solar salt-containing wastewater evaporation system based on dry-wet composite channels comprises: Figure 1

[0033] a feed liquid tank 1 for storing salt water;

[0034] a regenerator 3 for heat exchange between the wet air and the salt water from the feed liquid tank 1 to warm up the salt water;

[0035] and a dry-wet composite channel humidifier 5 comprising a shell 501 with an inner cavity, the upper end of the shell 501 is provided with a high-temperature liquid inlet for connecting the inner cavity with the high-temperature liquid outlet of the regenerator 3 and a high-temperature gas inlet for connecting the inner cavity with the high-temperature gas outlet of the regenerator 3, and the lower end is provided with an air inlet and a liquid outlet connected with the inner cavity;

[0036] The inner cavity is provided with a plurality of composite channels 502 arranged side by side and open at the lower end for air to enter, and each composite channel 502 comprises a dry channel 5021 closed at the upper end and a wet channel 5022 open at the upper end for liquid to flow in, and a longitudinal porous partition 5023 is arranged between the dry channel 5021 and the wet channel 5022, the longitudinal porous partition 5023 is provided with a plurality of communication holes along the longitudinal direction for connecting the dry channel 5021 and the wet channel 5022. A baffle 5024 is installed at the upper end of the dry channel 5021 for closing the upper end thereof, so as to ensure that the salt water entering from the high-temperature liquid inlet does not flow into the dry channel 5021, and at the same time, the air in the dry channel 5021 can all flow into the wet channel 5022, and finally continue to flow upward through the upper end opening of the wet channel 5022, and finally flow out of the dry-wet composite channel humidifier 5;

[0037] Firstly, the salt water in the feed liquid tank 1 enters the regenerator 3 to exchange heat with the wet hot air from the dry-wet composite channel humidifier 5 to warm up the salt water, and then is transported into the dry-wet composite channel humidifier 5, while the outside air enters the dry-wet composite channel humidifier 5 from the air inlet, directly contacts the hot salt water to exchange heat and mass, the temperature of the salt water decreases and part of the water evaporates, the concentrated salt water is discharged from the dry-wet composite channel humidifier 5 through the liquid outlet, the air is warmed and humidified, and then flows into the regenerator 3 to preheat the flowing cold salt water;

[0038] ​Part of the outside air flowing into the dry-wet composite channel humidifier 5 enters the dry channel 5021, and part of the air enters the wet channel 5022. The air flows upwards along the channels, as shown in Figure 2 The air in the wet channel 5022 exchanges heat and mass with the salt water in the wet channel 5022, and the temperature and humidity of the air gradually increase. The air in the dry channel 5021 exchanges heat with the salt water on the wall of the wet channel 5022 through the partition 5023, and the temperature of the air in the dry channel 5021 also gradually increases. At the same time, the air in the dry channel 5021 continuously flows into the wet channel 5022 through the communication holes in the partition 5023, mixes with the air in the wet channel 5022, and thus reduces the humidity of the air in the wet channel 5022. The air flow in the dry channel 5021 gradually decreases along the height direction, and the air flow in the wet channel 5022 gradually increases along the height direction.

[0039] In some examples, a solar collector 4 for heating the salt water flowing out of the high-temperature outlet of the regenerator 3 is arranged between the high-temperature outlet of the regenerator 3 and the high-temperature inlet of the dry-wet composite channel humidifier 5. The solar collector 4 uses solar radiation to heat the salt water, and can also use other renewable energy sources or low-grade waste heat for heating, thereby reducing the consumption of fossil energy.

[0040] In some examples, a spraying device 503 for spraying the salt water is arranged above the composite channel 502 and communicates with the high-temperature inlet to spray the salt water into the inner cavity and then into each wet channel 5022.

[0041] In some examples, a demister 504 for removing liquid droplets carried in the air is arranged above the spraying device 503.

[0042] In some examples, the regenerator 3 has a low-temperature outlet for discharging the condensed water formed after the air exchanges heat, and a condensed water tank 9 is connected to the low-temperature outlet. The hot air exchanges heat with the cold salt water in the regenerator 3, preheats the incoming cold salt water, and the air temperature decreases, and the condensed water is discharged from the low-temperature outlet into the condensed water tank 9.

[0043] In some examples, the regenerator 3 has a low-temperature outlet for discharging the low-temperature air after heat exchange, and a gas-liquid separation tank 8 is connected to the low-temperature outlet. The liquid outlet of the gas-liquid separation tank 8 communicates with the condensed water tank 9. The air after cooling and dehumidification is further separated by the gas-liquid separator, and the generated condensed water is collected in the condensed water tank 9, and the air is discharged.

[0044] In some examples, the air inlet of the dry-wet composite channel humidifier 5 is connected with an air inlet pipe, and a fan 7 is arranged on the air inlet pipe. The fan inlet of the fan 7 is in communication with the atmosphere and / or the gas outlet of the gas-liquid separation tank 8. A part of the air dehumidified by the gas-liquid separator is discharged from the system, and a part of the air is returned to the front of the fan 7, mixed with fresh ambient air, and then reenters the system for circulation.

[0045] In some examples, a first valve 10 is arranged on the pipeline between the fan inlet and the atmosphere, and a second valve 11 is arranged between the fan inlet and the outlet of the gas-liquid separation tank 8. The proportion of the return air and the fresh air is adjusted according to the system operation requirement and by the opening degree of the first valve 10 and the second valve 11, so that the system can be switched to open circulation, closed circulation and semi-closed circulation. If it is necessary to increase the evaporation amount of the system, the fresh air flow is increased, and the limit state is open air circulation, in which the second valve 11 is closed. If it is necessary to increase the thermal efficiency of the system, the flow of the return air is increased, and the limit state is closed air circulation, in which the first valve 10 is closed. When the first valve 10 and the second valve 11 are opened at the same time, the system is in semi-closed circulation.

[0046] In some examples, the liquid tank 1 is in communication with the liquid outlet of the dry-wet composite channel humidifier 5, and a third valve 12 is arranged between the liquid tank 1 and the dry-wet composite channel humidifier 5. The concentrated salt water evaporated and concentrated from the liquid outlet of the dry-wet composite channel humidifier 5 enters the liquid tank 1 through the third valve 12, so that the proportion of the external salt water and the concentrated salt water entering the liquid tank 1 is adjusted, and the concentration of the salt water in the liquid tank 1 is adjusted.

[0047] In some examples, a liquid pump 2 for conveying the salt water in the liquid tank 1 to the heat regenerator 3 is arranged between the liquid tank 1 and the heat regenerator 3. The liquid outlet of the dry-wet composite channel humidifier 5 is provided with a concentrated salt water pump 6.

[0048] Working principle:

[0049] External brine flows into the feed tank 1, mixes with a portion of the concentrated brine after evaporation and concentration, and is then pumped to the regenerator 3 by the feed pump 2. In the regenerator 3, the brine exchanges heat with the humid air, absorbing residual heat and increasing its temperature. It then flows into the solar collector 4 for further heating. The heated brine enters the wet-dry composite channel humidifier 5, spraying from the top into the wet channel 5022. It flows downwards along the wall, directly contacting the upward-flowing air for heat and mass transfer, increasing both temperature and humidity in the wet channel 5022. Simultaneously, some heat from the brine is indirectly transferred to the air in the dry channel 5021 through the partition 5023. The brine temperature decreases, some water evaporates, and the evaporated concentrated brine falls to the bottom of the wet-dry composite channel humidifier 5. It is then extracted by the concentrated brine pump 6, with a portion of the concentrated brine being directly discharged from the system and the other portion flowing back into the feed tank 1 to mix with fresh brine and re-enter the system for circulation. The mixing ratio of reflux brine to fresh brine is determined based on the required concentration of the brine after evaporation.

[0050] Ambient air enters the system through the air intake, mixes with the returning humid air, and is then delivered to the dry-wet composite channel humidifier 5 by the fan 7. The dry-wet composite channel humidifier 5 consists of several composite channels 502 arranged side-by-side; each dry-wet composite channel 502 comprises a dry channel 5021 and a wet channel 5022. A portion of the air flowing into the dry-wet composite channel 502 enters the dry channel 5021, while a portion enters the wet channel 5022. The air flows upwards along the channels, such as... Figure 2 As shown. Air in the wet channel 5022 undergoes heat and mass transfer with the brine within it, causing both its temperature and humidity to gradually increase. Air in the dry channel 5021 exchanges heat with the brine on the wall of the wet channel 5022 through the partition 5023, causing the air temperature in the dry channel 5021 to gradually increase as well. Simultaneously, air in the dry channel 5021 continuously flows into the wet channel 5022 through the connecting holes on the partition 5023, mixing with the air in the wet channel 5022 and thus reducing the humidity. The airflow rate in the dry channel 5021 gradually decreases along the height direction, while the airflow rate in the wet channel 5021 gradually decreases. The airflow rate within the 022 gradually increases along the height. After heat exchange, the air passes through the demister 504 to remove small droplets and finally flows out of the dry-wet composite channel humidifier 5. Subsequently, the humid air flows into the regenerator 3, preheating the incoming cold brine. The air temperature and humidity decrease, and condensate is produced. The cooled and dehumidified air then passes through the gas-liquid separator 8 for further condensate separation. All condensate produced is collected in the condensate tank 9. Part of the air cooled and dehumidified by the regenerator 3 is discharged from the system, while the other part flows back to the inlet of the fan 7, mixes with fresh outside air, and re-enters the dry-wet composite channel humidifier 5 for recirculation. The ratio of recirculated air to fresh air is switched between open circulation, closed circulation, and semi-closed circulation according to the system's operating requirements.

[0051] Within the wet-dry composite channel 502, the evaporation phase change (direct heat and mass transfer) occurs only within the wet channel 5022. The dry channel 5021 is a gas-liquid sensible heat transfer process (indirect heat transfer), with no mass transfer effect. The synergistic effect of indirect heat exchange in the dry channel 5021 and direct heat and mass transfer in the wet channel 5022 balances the heat and mass transfer during the dew point evaporation process. This causes the air temperature and enthalpy operating line during the dew point evaporation process to deviate from the saturation curve, reducing the heat and mass transfer difference during dew point evaporation, thereby reducing entropy increase and improving system thermal efficiency. Simultaneously, it allows the humid air temperature and enthalpy operating line within the regenerator 3 to approach a linear rather than an exponential curve, thus reducing the mismatch between the gas-liquid temperature and enthalpy operating lines within the regenerator 3, further reducing entropy increase and improving thermal efficiency. The temperature and enthalpy operating line of the evaporation system based on the wet-dry composite channel 502 is shown in Figure 3. The thermal efficiency of the evaporation system based on the wet-dry composite channel 502 can be increased by up to 34.6% compared to a conventional dew point evaporation system. Figure 4 As shown.

[0052] The above description, based on the preferred embodiments of the present invention, provides inspiration. Those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification but must be determined according to the claims.

Claims

1. A solar-powered saline wastewater evaporation system based on a dry-wet composite channel, characterized in that: include: Feed tank (1), used to store brine; A regenerator (3) is used to heat the humid air by exchanging heat with the brine from the feed tank (1); The dry-wet composite channel humidifier (5) includes a housing (501) with an inner cavity. The upper end of the housing (501) is provided with a high-temperature liquid inlet for connecting the inner cavity with the high-temperature liquid outlet of the regenerator (3) and a high-temperature air outlet for connecting the inner cavity with the high-temperature air inlet of the regenerator (3). The lower end is provided with an air inlet and a liquid outlet connected to the inner cavity. The inner cavity is provided with several parallel composite channels (502) with openings at the lower end for air to enter. Each composite channel (502) includes a dry channel (5021) with the upper end sealed and a wet channel (5022) with the upper end open for liquid to flow in. A longitudinal porous partition (5023) is provided between the dry channel (5021) and the wet channel (5022). The longitudinal porous partition (5023) has several connecting holes along the longitudinal direction for connecting the dry channel (5021) and the wet channel (5022). Both the dry channel (5021) and the wet channel (5022) have bottom openings to allow air to enter. At the same time, the air in the dry channel (5021) continuously flows into the wet channel (5022) through the connecting holes on the partition (5023), mixes with the air in the wet channel (5022), and balances the heat and mass transfer during the dew point evaporation process through the synergistic effect of indirect heat exchange in the dry channel (5021) and direct heat and mass transfer in the wet channel (5022).

2. The solar-powered saline wastewater evaporation system based on a dry-wet composite channel according to claim 1, characterized in that: A solar collector (4) is provided between the high-temperature outlet of the regenerator (3) and the high-temperature inlet of the dry-wet composite channel humidifier (5) for heating the brine flowing out of the high-temperature outlet of the regenerator (3).

3. The solar-powered saline wastewater evaporation system based on a dry-wet composite channel according to claim 1, characterized in that: Above the composite channel (502) is a spraying device (503) that is connected to a high-temperature liquid inlet to spray brine.

4. The solar-powered saline wastewater evaporation system based on a dry-wet composite channel according to claim 3, characterized in that: A demister (504) for removing droplets carried in the air is installed above the spray device (503).

5. The solar-powered saline wastewater evaporation system based on a dry-wet composite channel according to claim 1, characterized in that: The regenerator (3) has a low-temperature outlet for discharging the condensate formed after air heat exchange, and the low-temperature outlet is connected to a condensate tank (9).

6. The solar-powered saline wastewater evaporation system based on a dry-wet composite channel according to claim 5, characterized in that: The regenerator (3) has a low-temperature air outlet for discharging the low-temperature air after heat exchange. The low-temperature air outlet is connected to a gas-liquid separator (8), and the liquid outlet of the gas-liquid separator (8) is connected to a condensate tank (9).

7. A solar-powered saline wastewater evaporation system based on a dry-wet composite channel according to claim 6, characterized in that: The air inlet of the dry-wet composite channel humidifier (5) is connected to an air inlet pipe, and a fan (7) is provided on the air inlet pipe. The fan inlet of the fan (7) is connected to the atmosphere and / or the gas outlet of the gas-liquid separator (8).

8. A solar-powered saline wastewater evaporation system based on a dry-wet composite channel according to claim 7, characterized in that: A first valve (10) is installed on the pipeline between the fan inlet and the atmosphere, and a second valve (11) is installed between the fan inlet and the outlet of the gas-liquid separator (8).

9. A solar-powered saline wastewater evaporation system based on a dry-wet composite channel according to claim 1, characterized in that: The liquid tank (1) is connected to the drain port of the dry-wet composite channel humidifier (5), and a third valve (12) is provided between the two.

10. A solar-powered saline wastewater evaporation system based on a dry-wet composite channel according to claim 1, characterized in that: A feed pump (2) is provided between the feed tank (1) and the regenerator (3) to transport the brine in the feed tank (1) to the regenerator (3), and a concentrated brine pump (6) is provided at the drain port of the dry-wet composite channel humidifier (5).

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