CN113426257A - Wastewater recovery process and system based on low-grade heat source - Google Patents
Wastewater recovery process and system based on low-grade heat source Download PDFInfo
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/26—Drying gases or vapours
- B01D53/265—Drying gases or vapours by refrigeration (condensation)
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D47/00—Separating dispersed particles from gases, air or vapours by liquid as separating agent
- B01D47/06—Spray cleaning
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
- B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/26—Drying gases or vapours
- B01D53/261—Drying gases or vapours by adsorption
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/043—Details
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/10—Treatment of water, waste water, or sewage by heating by distillation or evaporation by direct contact with a particulate solid or with a fluid, as a heat transfer medium
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/16—Treatment of water, waste water, or sewage by heating by distillation or evaporation using waste heat from other processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/02—Other waste gases
- B01D2258/0283—Flue gases
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Abstract
A waste water recovery process and a system based on a low-grade heat source comprise the following steps: filling high-specific-surface-area hydrophilic fillers into the humidifying tower and the dehumidifying tower, and spraying the salt-containing wastewater from the top of the first stage humidifying tower to the interior of the humidifying tower after heat exchange and temperature rise; injecting hot flue gas from the side surface of the humidifying tower, contacting the hot flue gas with salt-containing wastewater and a hydrophilic filler with a high specific surface area in a cross-shaped cross flow manner in the humidifying tower for humidifying, carrying out isothermal vapor phase change and cooling to recover moisture in the hot flue gas, and obtaining recovered water; the method comprises the steps of spraying recovered water from the top of the dehumidification tower to the inside of the dehumidification tower, enabling hot flue gas to be in cross-flow contact with the recovered water and the high-specific-surface-area hydrophilic filler in the dehumidification tower, cooling and dehumidifying to obtain the recovered water and cooled flue gas, solving the technical problem that the recovery efficiency is low due to the fact that a recovery process is complex and recovery energy consumption is high in a traditional wastewater recovery method, and being widely applied to the technical field of wastewater recovery and recycling.
Description
Technical Field
The application relates to the technical field of wastewater recycling, in particular to a wastewater recycling process and system based on a low-grade heat source.
Background
Water is one of the most important natural resources on the earth, is an indispensable important resource in the life and production of people, and is an important element for promoting the sustainable development of the whole society and economy and promoting the progress of industrial civilization, however, underground water and fresh water which can be directly utilized by people unfortunately are not 0.36 percent of the total amount of the underground water and the fresh water, the total amount of Chinese water is 2.8 billion cubic meters and is listed in the 6 th position of the world, but the average water resource amount of people is only 25 percent of the average level in the world, the united nations are one of 13 countries which are listed as the most poor water in the world, and the average water resource amount of people is lower than 3000 cubic meters and is slightly water deficient according to the internationally recognized standard; the average water resource is moderate water shortage below 2000 cubic meters; the average water resource is less than 1000 cubic meters, and the water is severely deficient; the average water resource is less than 500 cubic meters, which is extremely water-deficient. At present, 16 provinces (districts and cities) in China have the per capita water resource amount (excluding the water passing through the border) lower than the serious water shortage line, and 6 provinces and districts (Ningxia, Hebei, Shandong, Henan, Shanxi and Jiangsu) have the per capita water resource amount lower than 500 cubic meters, and are regions with extreme water shortage. The urban water resource in China is extremely short and has wide related problems, the urban water shortage in China is 60 billion cubic meters every year, the economic loss caused by water shortage is about 2000-4000 billion yuan every year, and the related and affected fields comprise: the serious water shortage problem in industry, agriculture, construction industry, resident life and the like causes the modernized construction process of cities and towns, the increase of GDP and the improvement of the living standard of residents in China to be limited.
On the other hand, with the continuous expansion of urban scale and the rapid development of industry, the amount of discharged sewage is also increased, the water quality is deteriorated, and the water body is polluted, thereby affecting the sustainable utilization of water resources. Urban areas and industrial pollution sources are characterized by multiple discharge points, various types of discharged sewage, high discharge intensity, strong liquidity and easy pollution to other water resources, and even if local pollution occurs, the pollution range is gradually enlarged due to the liquidity of water. At present, the concentrated treatment of the total discharge of industrial and urban sewage in China accounts for less than half of the total discharge, most of the rest sewage is directly discharged into rivers, the restriction on the discharge of sewage is not large, and a large amount of water resources are deteriorated. Relevant experts in China analyze that the total water demand of 2050 years in China is 8000 hundred million, and at least 2400 hundred million cubic meters is increased than the current water demand, so that the sustainable development of national economy can be guaranteed. Therefore, the water is greatly saved and the reuse rate of the waste water is improved.
The sea water desalination and ocean chemical industry have unique advantages in coastal water-deficient cities and areas, the membrane separation sea water desalination technology still remains an important development direction of sea water desalination at present, but the key technology of sea water desalination still needs to break through, three key cores, namely, energy recovery, high-pressure pump and membrane material technology and equipment, still are made by people and belong to the technology of 'neck clamping', so that the sea water desalination technology in China and Shandong province has high investment, low income and difficult large-scale popularization, and the novel sea water desalination technology for humidifying and dehumidifying by using the novel high-specific surface area hydrophilic material does not need the high-pressure pump and the membrane material, namely, the sea water desalination technology for utilizing waste heat and efficiently separating and condensing gas and liquid can be applied to occasions such as islands, ships, factories and the like.
Humidification-dehumidification type waste water recovery technology is considered as one of promising technologies, at present, most humidification-dehumidification processes utilize a heat source to make hot waste water contact with flowing flue gas so as to humidify the flue gas, then wet flue gas is indirectly condensed by cooling water so as to generate fresh water, or hot flue gas and waste water contact with water flue gas in a packed tower so as to become saturated water vapor flue gas, then wet flue gas is indirectly condensed by cooling water so as to generate fresh water, and Q & ltKA (T-T & gtKA (T-K) according to Newton's cooling theorem is large in heat consumption in the humidification-dehumidification process0) (Q is a heat transfer amount; k is the heat transfer coefficient; a is the heat transfer area; T-T0For heat transfer temperature difference), in order to improve the efficiency of mass transfer and heat transfer, the larger the packing area in the packed tower is, the better the packing area is, and the more hydrophilic the packing area is; the design of the packed tower is very important, and the Re number and K are improved as much as possible; meanwhile, the adsorption material for recovering saturated water vapor in the flue gas is very important, and in order to improve the performance coefficient of the system, the multi-stage and multi-effect recovery of heat energy and saturated water vapor is also a main means, so that the aim of recovering the saturated water vapor and the saturated water vapor is fulfilledThe invention relates to a humidifying-dehumidifying type salt-containing wastewater recovery process of a hydrophilic filler with a high specific surface area and a low-grade heat source, which is used for further improving the wastewater recovery efficiency and has important practical and strategic significance.
Disclosure of Invention
The application aims to provide a low-grade heat source-based wastewater recovery process and system, and aims to solve the technical problem that the recovery efficiency is low due to the fact that the recovery process is complex and the recovery energy consumption is high in the traditional wastewater recovery method.
The first aspect of the embodiment of the application provides a wastewater recovery process based on a low-grade heat source, which is used for recovering salt-containing wastewater and hot flue gas and comprises the following steps:
s1, filling high-specific-surface-area hydrophilic fillers into the humidifying tower and the dehumidifying tower, heating the salt-containing wastewater, and spraying the salt-containing wastewater into the humidifying tower from the top of the humidifying tower;
s2, injecting the hot flue gas from the side face of the humidifying tower, wherein the hot flue gas, the salt-containing wastewater and the hydrophilic filler with the high specific surface area are in cross-flow contact humidification in the humidifying tower, isothermal water vapor phase change is carried out, and moisture in the hot flue gas is cooled and recovered to obtain recovered water;
s3, spraying the recovered water to the inside of the dehumidification tower from the top of the dehumidification tower, and carrying out cross flow contact on the hot flue gas, the recovered water and the hydrophilic filler with the high specific surface area in the dehumidification tower to carry out cooling and dehumidification so as to obtain the recovered water and the cooled flue gas.
In one embodiment, the humidifying tower and the dehumidifying tower are at least two, and the recovered water obtained by the S3 and the cooled flue gas are recycled and recovered by repeating the steps S1, S2 and S3.
In one embodiment, the high specific surface area hydrophilic filler is a high specific surface area structured filler net, the diameter of the mesh wire of the high specific surface area structured filler net is 1mm, and the mesh number is 80-120 meshes.
In one embodiment, the surface of the high specific surface area structured packing mesh is coated withAl2O3-MnO2And (c) a complex.
In one embodiment, the high specific surface area hydrophilic filler has a specific surface area of 2500m2/m3Bulk density of 320-650 kg/m3The void ratio is 70-90%, the F factor is 1.5-3.5, the wave pitch is 10-55 mm, and the tooth form angle is 30-80.
In one embodiment, the temperature of the salt-containing wastewater is raised by a heat exchanger, and the salt-containing wastewater is heated by the heat exchanger and then is sprayed from the top of the humidifying tower to the inside of the humidifying tower.
A second aspect of the embodiment of the application provides a waste water recovery system based on low-grade heat source, including humidification tower and dehumidification tower, the inside of humidification tower and the inside of dehumidification tower all are equipped with the regular packing net of high specific surface area, the top of humidification tower is equipped with the waste water entry, the top of dehumidification tower is equipped with the recovery water entry, the bottom of humidification tower with the bottom of dehumidification tower all is equipped with the recovery water export, humidification tower with the outside of dehumidification tower is equipped with heat exchanger and recovery water storage tank, the heat exchanger with waste water entry intercommunication, the recovery water export with recovery water storage tank intercommunication.
In one embodiment, the humidifying tower and the dehumidifying tower are provided in at least two.
In one embodiment, the high specific surface area structured packing mesh is disposed at an inclination of 45 ° inside the humidifying tower and the dehumidifying tower.
In one embodiment, the surface of the high specific surface area structured packing net is provided with a falling film collecting pipe, and the falling film collecting pipe is made of hydrophobic materials such as polypropylene or polytetrafluoroethylene with the diameter of 3-4 mm.
Compared with the traditional humidification-dehumidification method, the low-grade heat source-based wastewater recovery process and system provided by the invention have the advantages that the specific surface area is up to 2500m2/m3The surface of the hydrophilic regular catalytic packing is coated with a hydrophilic compound, so that the hydrophilic regular catalytic packing has the advantages of high void ratio, good hydrophilic wettability, small pressure drop, large flux, long service life and fast mass and heat transfer; and in the hot flue gas containing saturated water vaporBefore the dehumidification tower is contacted with the dehumidification tower, an isothermal steam phase change capture steam inclined plate of a high specific surface area regular packing net is used, so that the recycled fresh water amount is improved, the efficiency of the humidification dehumidification tower is improved, the humidification dehumidification tower is manufactured by acrylic or PPR, the manufacturing cost of the humidification dehumidification tower is reduced, the dehumidification tower is resistant to wastewater corrosion, and the operation condition in the tower is convenient to observe; the hot flue gas is contacted with the salt-containing wastewater in a cross-flow manner, so that the pressure loss of flue gas operation is reduced, and an induced draft fan is not required to be additionally arranged; the heat exchanger is arranged outside the humidifying and dehumidifying tower, so that the maintenance and the adjustment of the area of the heat exchange module are facilitated; the technical scheme of the application can obviously reduce the manufacturing cost of the humidifying and dehumidifying tower and the recycling and operating cost of the wastewater, and the recovery rate of the salt-containing wastewater can reach 50-70%.
Drawings
FIG. 1 is a schematic flow diagram of a low-grade heat source-based wastewater recovery process provided by an embodiment of the present application;
fig. 2 is a schematic structural diagram of a wastewater recovery system based on a low-grade heat source according to an embodiment of the present application.
The symbols in the drawings illustrate that:
1. a first humidifying tower; 2. a first dehumidification tower; 3. a structured packing net with high specific surface area; 4. a wastewater inlet; 5. a reclaimed water inlet; 6. a first recovered water outlet; 7. a second recovered water outlet; 8. a heat exchanger; 9. a reclaimed water storage tank; 10. a second humidification tower; 11. a second dehumidification tower; 12. a waste water pump; 13. a fresh water pump; 14. and (4) a chimney.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
The traditional humidifying-dehumidifying type salt-containing wastewater recovery process usually adopts random packing and metal or ceramic regular packing; generally, these structured packings have a maximum specific surface area of not more than 700m2/m3Surface hydrophilic modification is not intentionally made; according to the mass transfer theory，Q＝kda(C0-Ct) I.e. in the concentration difference (C)0-Ct) Under certain conditions, the mass transfer rate and the mass transfer coefficient kdProportional to the specific surface area a per unit volume of the filler, that is, the higher the specific surface area of the filler, the faster the mass transfer rate; on the other hand, the mass transfer coefficient kdThe Re number is related to the Re number of the fluid and the thickness of a Plant boundary layer, and is closely related to the hydrophilicity (liquid holdup) of the surface of the filler, when the filler has strong hydrophilicity, the liquid holdup of the surface of the filler is large, the mass transfer is fast, and the high Re number can not cause the occurrence of flooding, so that the operation is deteriorated; meanwhile, the traditional filler has no hydrophilic function, so that the gas-liquid mass transfer rate of hot flue gas and spray wastewater on the surface of the filler only depends on the mass transfer rate and the gas-liquid equilibrium theorem.
Referring to fig. 1, a schematic flow chart of a wastewater recycling process based on a low-grade heat source according to an embodiment of the present application is shown, and for convenience of illustration, only the relevant portions of the embodiment are shown, which is described in detail as follows:
in one embodiment, the first aspect of the present application provides a wastewater recovery process based on a low-grade heat source, which is used for performing recovery treatment on saline wastewater and hot flue gas, and comprises the following steps:
and S1, filling high-specific-surface-area hydrophilic fillers into the humidifying tower and the dehumidifying tower, heating the salt-containing wastewater, and spraying the salt-containing wastewater into the humidifying tower from the top of the humidifying tower.
Specifically, the humidifying tower and the dehumidifying tower are at least two, high specific surface area hydrophilic fillers are filled in the humidifying tower and the dehumidifying tower, the high specific surface area hydrophilic fillers are high specific surface area regular filler nets, the high specific surface area regular filler nets are arranged in the humidifying tower and the dehumidifying tower in an inclined manner of 45 degrees, the length of the high specific surface area regular filler nets is 300mm, the widths of the high specific surface area regular filler nets are the same as those of the humidifying tower and the dehumidifying tower, the diameters of net wires of the high specific surface area regular filler nets are 1mm, the mesh number is 80-120 meshes, and the surfaces of the high specific surface area regular filler nets are coated with Al2O3-MnO2Composite, falling film collecting pipe and condensed fresh water pipe, high specific surface area hydrophilic fillerIs 2500m2/m3Bulk density of 320-650 kg/m3The void ratio is 70-90%, the F factor is 1.5-3.5, the wave pitch is 10-55 mm, and the tooth form angle is 30-80; after the temperature of the salt-containing wastewater with the temperature of 20-30 ℃ is raised to 30-40 ℃ by a heat exchanger, pumping the salt-containing wastewater into the top of the humidifying tower by a wastewater pump and spraying the salt-containing wastewater into the humidifying tower.
S2, injecting hot flue gas from the side face of the humidifying tower, and carrying out cross-flow contact humidification on the hot flue gas, the saline wastewater and the hydrophilic filler with the high specific surface area in the humidifying tower, so as to carry out isothermal vapor phase change and cooling to recover moisture in the hot flue gas and obtain recovered water.
Specifically, hot flue gas is generally waste flue gas discharged by a factory, hot flue gas at 70-130 ℃ is injected into a humidifying tower from the side surface of the humidifying tower, the hot flue gas in cross flow is in cross flow contact with a hydrophilic regular catalytic packing with a high specific surface area in the humidifying tower for humidifying, isothermal water vapor phase change and cooling are carried out on the net surface of a regular packing net with a high specific surface area for recovering moisture in the hot flue gas, fresh water recovered water is obtained, and the recovered moisture falls into a free falling body and enters a recovered water storage tank.
And S3, spraying the recovered water from the top of the dehumidification tower to the inside of the dehumidification tower, and carrying out cross flow contact on the hot flue gas, the recovered water and the hydrophilic filler with the high specific surface area in the dehumidification tower to carry out cooling and dehumidification so as to obtain the recovered water and the cooled flue gas.
Specifically, the recovered water is sprayed from the top of the dehumidification tower to the inside of the dehumidification tower through a fresh water pump, the hot flue gas, the recovered water and the hydrophilic filler with high specific surface area are in cross-flow contact with each other in the dehumidification tower to cool and dehumidify, the temperature of the hot flue gas is reduced by 15-20 ℃, a recycling treatment cycle (namely a first effect) is completed, then the hot flue gas enters a second effect, the obtained recovered water and cooled flue gas are recycled and recycled in steps S1, S2 and S3, and multiple effects can be performed by analogy until the temperature of the flue gas is reduced to 30 ℃ and the flue gas is discharged through a chimney; the temperature difference between the flue gas of the humidifying tower and the flue gas of the dehumidifying tower of each effect is 15 ℃, the theoretical maximum dehumidifying rate varies from 39% to 55% along with the temperature, but the absolute dehumidifying water amount is gradually reduced from high temperature to low temperature.
In the embodiment, the design of the humidifying-dehumidifying tower is 5 effects, the temperature of hot flue gas is 100 ℃, the temperature of each effect is reduced by 15 ℃, the flue gas is discharged into a chimney when the temperature is 25 ℃, the flow rate of the hot flue gas is 3500Nm3/h, and the linear velocity of the hot flue gas entering the tower is about 1.0 m/s; the temperature of the salt-containing wastewater is 20 ℃, the flow of the treated wastewater is 30m3/h, normal-temperature water can be injected into a recovered water storage tank when the system is started, and then the temperature of the cooled recovered water is maintained not to exceed 25 ℃; after 1 week of operation, the operating cost (electricity consumption) and the wastewater recovery rate were measured, and the results are shown in Table 1.
TABLE 1 Hot flue gas and high specific surface area hydrophilic structured packing humidifying-dehumidifying tower waste water recovery process parameters
Therefore, the cost per ton of wastewater recovery is very low, which is lower than 4.9 yuan/ton, and the investment cost is very low due to the normal pressure operation of the humidifying-dehumidifying tower and the plastic manufacturing.
Referring to fig. 2, a schematic structural diagram of a waste water recycling system based on a low-grade heat source according to an embodiment of the present application is shown, for convenience of description, only the relevant portions of the embodiment are shown, and the details are as follows:
the second aspect of the embodiment of the application provides a waste water recovery system based on low-grade heat source, including humidifying tower and dehumidification tower, humidifying tower's inside and dehumidification tower's inside all are equipped with high specific surface area regular packing net 3, humidifying tower's top is equipped with waste water entry 4, dehumidification tower's top is equipped with recovery water entry 5, humidifying tower's bottom is equipped with first recovery water export 6, dehumidification tower's bottom is equipped with second recovery water export 7, humidifying tower and dehumidification tower's outside is equipped with heat exchanger 8 and recovery water storage tank 9, heat exchanger 8 and waste water entry 4 intercommunication, first recovery water export 6 and second recovery water export 7 all communicate with recovery water storage tank 9.
Specifically, the humidifying tower and the dehumidifying tower are at least two, two groups of humidifying and dehumidifying towers are arranged in the drawing of the embodiment, namely a first humidifying tower 1, a first dehumidifying tower 2, a second humidifying tower 10 and a second dehumidifying tower 11, the humidifying tower and the dehumidifying tower are made of acrylic, polypropylene (PPR) or plastics, the strong corrosion resistance of the acrylic, the polypropylene (PPR) or the plastics is utilized, the manufacturing cost of the humidifying-dehumidifying tower is saved, and when the acrylic is adopted, the gas-liquid contact mass transfer and heat transfer operation conditions in the towers can be observed due to the transparency of the acrylic; the humidifying tower and the dehumidifying tower are both designed into rectangular towers, and the size is as follows: the length, width and height are 1000, 1200 and 1000, so that the linear speed of hot flue gas entering the humidifying tower and the dehumidifying tower is reduced, the pressure drop is reduced, and the flue gas after temperature reduction and dehumidification is directly discharged through a chimney without arranging an induced draft fan.
The humidifying tower and the dehumidifying tower are internally provided with the high specific surface area regular packing net 3, the high specific surface area regular packing net 3 is obliquely arranged at 45 degrees in the humidifying tower and the dehumidifying tower, the length of the high specific surface area regular packing net 3 is 300mm, the width of the high specific surface area regular packing net 3 is the same as that of the humidifying tower and the dehumidifying tower, the diameter of a mesh wire of the high specific surface area regular packing net 3 is 1mm, the mesh number is 80-120 meshes, and the surface of the high specific surface area regular packing net 3 is coated with Al2O3-MnO2The falling film collecting pipe is a hollow pipe made of hydrophobic materials such as polypropylene or polytetrafluoroethylene with the diameter of 3-4mm, the outer wall of the hollow pipe is provided with a groove for facilitating falling film flow of water drops, meanwhile, the hydrophobicity of the falling film collecting pipe is good, the water drops are in a laminar flow fluid state on the surface, the heat exchanger 8 is arranged outside and is convenient to maintain, the falling film collecting pipe is connected with a low-temperature water pipe of the heat exchanger 8 and can play a role in slight temperature reduction and liquid seal, and the temperature of collected recycled water is 3-10 ℃ lower than that of flue gas, so that part of phase change water and condensed water can be recovered by the design of the falling film collecting pipe, the fresh water spraying amount of a humidifying tower is reduced, meanwhile, steam phase change heat is transferred to hot flue gas, the temperature of the hot flue gas is basically not reduced, but the recycled water amount is increased; the high specific surface area regular packing net 3 has hard surface and permeability function, when hot flue gas containing saturated water vapor passes through, water vapor fog beads can rotate around the surface of the net wire in a laminar flow state to be condensed, and under the combined action of phase change at the same temperature and low-temperature condensation, water is collected and then enters a humidifying tower or a dehumidifying tower.
After the temperature of the salt-containing wastewater is raised by a heat exchanger 8, the salt-containing wastewater is pumped into the first humidifying tower 1 from a wastewater inlet 4 by a wastewater pump 12, the salt-containing wastewater and hot flue gas entering from the side surface in a cross-flow manner are in cross-flow contact humidification in a high specific surface area regular packing net 3 in the first humidifying tower 1, isothermal water vapor phase change and cooling are carried out on the net surface of the high specific surface area regular packing net 3 to recover moisture in the flue gas to obtain recovered water, the recovered water enters a recovered water storage tank 9 through a first recovered water outlet 6, the recovered water in the recovered water storage tank 9 is sprayed from a recovered water inlet 5 at the top of the first dehumidifying tower 2 to the inside of the first dehumidifying tower 2 through a fresh water pump 13, the hot flue gas discharged by the first humidifying tower 1 is in cross-flow contact with the recovered water and hydrophilic packing with the high specific surface area in the dehumidifying tower to carry out temperature reduction and dehumidification, at the moment, the temperature of the hot flue gas is reduced by 15-20 ℃, the obtained recovered water enters the heat exchanger 8 through a second recovered water outlet 7, completing a recycling treatment cycle (namely one effect), and then entering a second effect, namely repeating the recycling treatment of the steps S1, S2 and S3 through the second humidifying tower 10 and the second dehumidifying tower 11, and so on, so as to carry out multiple effects until the temperature of the flue gas is reduced to 30 ℃ and the flue gas is discharged through a chimney 14.
In conclusion, compared with the traditional humidification-dehumidification method, the low-grade heat source-based wastewater recovery process and system provided by the invention have the advantages that the specific surface area is as high as 2500m2/m3The surface of the hydrophilic regular catalytic packing is coated with a hydrophilic compound, so that the hydrophilic regular catalytic packing has the advantages of high void ratio, good hydrophilic wettability, small pressure drop, large flux, long service life and fast mass and heat transfer; before the hot flue gas containing saturated steam contacts the dehumidification tower and the dehumidification tower, an isothermal steam phase change capture steam inclined plate of a high specific surface area regular packing net is used, so that the recycled fresh water is improved, the efficiency of the humidification dehumidification tower is improved, the humidification dehumidification tower is made of acrylic or PPR, the manufacturing cost of the humidification dehumidification tower is reduced, the humidification dehumidification tower is resistant to wastewater corrosion, and the operation condition in the tower can be observed conveniently; the hot flue gas is contacted with the salt-containing wastewater in a cross-flow manner, so that the pressure loss of flue gas operation is reduced, and an induced draft fan is not required to be additionally arranged; the heat exchanger is arranged outside the humidifying and dehumidifying tower, so that the maintenance and the adjustment of the area of the heat exchange module are facilitated; the technical scheme of the application can obviously reduce the manufacturing cost of the humidifying and dehumidifying tower and the recycling and operating cost of the wastewater, and the salt-containing wastewaterThe recovery rate can reach 50-70%, and the technical scheme provided by the application can also be used for humidifying and dehumidifying seawater desalination of ship flue gas.
Various embodiments are described herein for various devices, circuits, apparatuses, systems, and/or methods. Numerous specific details are set forth in order to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. However, it will be understood by those skilled in the art that the embodiments may be practiced without such specific details. In other instances, well-known operations, components and elements have been described in detail so as not to obscure the embodiments in the description. It will be appreciated by those of ordinary skill in the art that the embodiments herein and shown are non-limiting examples, and thus, it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.
Claims (10)
1. A wastewater recovery process based on a low-grade heat source is used for recovering salt-containing wastewater and hot flue gas, and is characterized by comprising the following steps:
s1, filling high-specific-surface-area hydrophilic fillers into the humidifying tower and the dehumidifying tower, heating the salt-containing wastewater, and spraying the salt-containing wastewater into the humidifying tower from the top of the humidifying tower;
s2, injecting the hot flue gas from the side face of the humidifying tower, wherein the hot flue gas, the salt-containing wastewater and the hydrophilic filler with the high specific surface area are in cross-flow contact humidification in the humidifying tower, isothermal water vapor phase change is carried out, and moisture in the hot flue gas is cooled and recovered to obtain recovered water;
s3, spraying the recovered water to the inside of the dehumidification tower from the top of the dehumidification tower, and carrying out cross flow contact on the hot flue gas, the recovered water and the hydrophilic filler with the high specific surface area in the dehumidification tower to carry out cooling and dehumidification so as to obtain the recovered water and the cooled flue gas.
2. The wastewater recovery process based on low-grade heat source according to claim 1, characterized in that the humidifying tower and the dehumidifying tower are at least two, and the recovered water obtained from S3 and the cooled flue gas are recycled and recovered by repeating the steps S1, S2 and S3.
3. The waste water recovery process based on low-grade heat source according to claim 1, characterized in that the high specific surface area hydrophilic filler is a high specific surface area structured filler net, the diameter of the net wire of the high specific surface area structured filler net is 1mm, and the mesh number is 80-120 meshes.
4. The low-grade heat source-based wastewater recovery process according to claim 1, wherein the surface of the high specific surface area structured packing net is coated with Al2O3-MnO2And (c) a complex.
5. The process for recovering waste water based on low-grade heat source according to claim 1, wherein the high specific surface area hydrophilic filler has a specific surface area of 2500m2/m3Bulk density of 320-650 kg/m3The void ratio is 70-90%, the F factor is 1.5-3.5, the wave pitch is 10-55 mm, and the tooth form angle is 30-80.
6. The process for recovering the wastewater based on the low-grade heat source according to claim 1, wherein the temperature of the salt-containing wastewater is raised by a heat exchanger, and the salt-containing wastewater is sprayed from the top of the humidifying tower to the inside of the humidifying tower after being raised by the heat exchanger.
7. The utility model provides a waste water recovery system based on low-grade heat source, includes humidifying tower and dehumidification tower, the inside of humidifying tower and the inside of dehumidification tower all are equipped with the regular packing net of high specific surface area, the top of humidifying tower is equipped with the waste water entry, the top of dehumidification tower is equipped with the recovery water entry, the bottom of humidifying tower with the bottom of dehumidification tower all is equipped with the recovery water export, humidifying tower with the outside of dehumidification tower is equipped with heat exchanger and recovery water storage tank, the heat exchanger with waste water entry intercommunication, the recovery water export with recovery water storage tank intercommunication.
8. The low-grade heat source-based wastewater recovery system according to claim 7, wherein the humidifying tower and the dehumidifying tower are provided in at least two.
9. The low-grade heat source-based wastewater recovery system according to claim 7, wherein the high specific surface area structured packing net is disposed at an inclination of 45 ° inside the humidifying tower and the dehumidifying tower.
10. The waste water recovery system based on low-grade heat source according to claim 7, characterized in that the surface of the high specific surface area structured packing net is provided with a falling film collecting pipe, and the falling film collecting pipe is made of hydrophobic material such as polypropylene or polytetrafluoroethylene with a diameter of 3-4 mm.
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