CN115925040A - High-salinity water treatment process and system based on cyclone reinforcement - Google Patents
High-salinity water treatment process and system based on cyclone reinforcement Download PDFInfo
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- CN115925040A CN115925040A CN202310231443.0A CN202310231443A CN115925040A CN 115925040 A CN115925040 A CN 115925040A CN 202310231443 A CN202310231443 A CN 202310231443A CN 115925040 A CN115925040 A CN 115925040A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Abstract
The invention belongs to the technical field of seawater desalination, and particularly relates to a high-salinity water treatment process and system based on cyclone reinforcement. The system comprises a seawater storage tank, a delivery pump, a refrigerating device, a fresh water storage tank, a crystallized salt storage tank, a cyclone separator and a medium removing sieve; the process comprises the steps of carrying out secondary refrigeration on seawater, feeding the seawater which is subjected to suspension crystallization and ultrasonic wave auxiliary refrigeration to meet the medium condition of cyclone separation into a primary cyclone separator, removing high salt water in salt cells, feeding a product after tertiary refrigeration into a secondary cyclone separator, finally obtaining pure water ice crystals and saturated salt water from an overflow pipe outlet of the secondary cyclone separator, obtaining crystallized salt and saturated salt water from a bottom flow outlet, and further obtaining the pure water ice crystals and the crystallized salt through a medium removal sieve, thereby realizing the efficient recovery of fresh water resources, solving the problems of large occupied area of a system, large process energy consumption, complex flow, use of chemical preparations and the like in the prior art, and being suitable for large-scale application of ocean offshore platforms or offshore cities.
Description
Technical Field
The invention belongs to the technical field of seawater desalination, and particularly relates to a high-salinity water treatment process and system based on rotational flow reinforcement.
Background
The existing seawater desalination process generally uses a distillation method and a reverse osmosis method, but the distillation method has the problems of high boiling point, high energy consumption, serious corrosion and scaling, high equipment investment, operation and maintenance cost and the like, and the reverse osmosis technology has large osmotic pressure and large operation pressure, so that the investment and operation cost is increased, and even the concentration of part of high-concentration salt seawater exceeds the upper limit of the reverse osmosis technology. In contrast, the low-temperature freezing crystallization method is a seawater desalination treatment method with good application prospect, the desalination rate reaches more than 99.5%, and the method has unique advantages. Firstly, the melting latent heat of ice under normal pressure is 334 kJ/kg, which is far lower than the vaporization latent heat of water 2259.4 kJ/kg, so that compared with a thermal method, the energy consumption of the desalting process by a low-temperature crystallization method is greatly reduced; secondly, the operation at low temperature can greatly reduce the corrosion to equipment materials and avoid the problem of scaling; finally, the low-temperature crystallization method does not need to add any chemical reagent, thereby avoiding secondary pollution and being an environment-friendly technology.
The main reasons for limiting the large-scale application of the freezing method seawater desalination technology at present are as follows: when the seawater is frozen, pure water in the seawater is condensed into ice crystals, and salt which is not discharged is wrapped in gaps of the ice crystals in a concentrated saline water mode. With the aggregation and growth of ice crystal particles, pure water cannot be obtained by a pure freezing method due to the existence of 'salt cells' in the ice crystals, and the product ice needs to be subjected to secondary treatment, so that the complexity of the process flow is increased.
Disclosure of Invention
The invention aims to solve the technical problem of providing a high-salinity water treatment process and system based on rotational flow reinforcement. The technical scheme is as follows:
a high-salinity water treatment system based on rotational flow strengthening comprises a seawater storage tank, a delivery pump, a refrigerating device, a fresh water storage tank, a crystallized salt storage tank, a rotational flow separator and a medium removing sieve; the seawater storage tank is connected with a first delivery pump through a delivery pipe and then connected with a primary refrigerating device through the delivery pipe; the first-stage refrigerating device is connected with the second-stage refrigerating device through a second conveying pump and a conveying pipe, and the second-stage refrigerating device is connected with the first-stage cyclone separator through a third conveying pump and a conveying pipe; the top end of the first-stage cyclone separator is connected with a third-stage refrigerating device through a fourth conveying pump and a conveying pipe, the bottom end of the first-stage cyclone separator is connected with a first medium removing sieve through the conveying pipe, a product at one end of the first medium removing sieve enters the first-stage refrigerating device, and a product at the other end of the first medium removing sieve enters the third-stage refrigerating device through the fourth conveying pump; the tertiary refrigerating device is connected with the second-stage cyclone separator, the top end of the second-stage cyclone separator is connected with the second medium removing sieve through the conveying pipe and the fifth conveying pump, the bottom end of the second-stage cyclone separator is connected with the third medium removing sieve through the conveying pipe, a product at one end of the third medium removing sieve enters the crystallized salt storage box, a product at the other end of the third medium removing sieve returns to the tertiary refrigerating device through the fourth conveying pump, the product at one end of the second medium removing sieve enters the primary refrigerating device, and the product at the other end of the second medium removing sieve enters the tertiary refrigerating device through the fourth conveying pump.
Preferably, the primary refrigerating device comprises an ice crystal storage barrel for containing fresh water ice crystals, the outer side of the ice crystal storage barrel is sequentially wound with a plurality of circles of conveying pipes for conveying seawater from top to bottom, an ice crystal port is formed in the top end of the ice crystal storage barrel, a freezing outlet is formed in the bottom of the lower side of the ice crystal storage barrel, seawater in the conveying pipes can be cooled to 6-8 ℃ through heat exchange with the fresh water ice crystals in the ice crystal storage barrel, and the fresh water ice crystals are melted.
Preferably, the products of the first medium removing sieve and the second medium removing sieve entering the first-stage refrigerating device are fresh water ice crystals which are directly placed in an ice crystal storage barrel through ice crystal openings.
Preferably, the secondary refrigerating device comprises a freezing cavity, a feed inlet is arranged on the upper side of one end of the freezing cavity, a discharge outlet is arranged on the lower side of the other end of the freezing cavity, and refrigerating gas pipelines which are closely arranged in an s shape are arranged on the periphery of the freezing cavity; stirring blades are arranged in the freezing cavity, comprise a plurality of large blades and small blades and are arranged in a crossed manner; an ultrasonic auxiliary refrigerating instrument is arranged outside the freezing cavity to improve the phase change temperature of liquid drops, ultrasonic waves are uniformly and densely surrounded around the freezing cavity, and the temperature is kept within the range of-10 ℃ to-7 ℃. The third-stage refrigerating device is the same as the second-stage refrigerating device.
Preferably, the stirring speed of the large paddle is 200 r/min and the large paddle rotates anticlockwise so as to control the flow of the two-phase fluid; the stirring speed of the small blades is 50 r/min and the small blades rotate clockwise so as to prevent ice crystals from approaching the side wall of the freezing cavity to cause ice crystal retention; the frequency of the ultrasonic auxiliary refrigeration instrument is set to 20000 HZ, and the ultrasonic intensity is set to 800W/m 2 。
Preferably, the upper side end of the first-stage cyclone separator is provided with a cyclone inlet, the center of the inside of the upper side is provided with an overflow pipe, an arc-shaped downward-inclined guide plate is arranged between the cyclone inlet and the overflow pipe, the outlet of the overflow pipe is arranged at the top end of the first-stage cyclone separator, the bottom end of the overflow pipe is provided with a cyclone underflow port, and the inside of the overflow pipe is also provided with a central screen; the center screen is arranged next to the cyclone inlet, the uppermost end of the center screen is fixedly connected with the inner wall of the shell of the first-stage cyclone separator, and the center screen is downwards separated from the inner wall of the shell of the first-stage cyclone separator at a certain distance; the central screen mesh is provided with screen holes with the size of 40 +/-5 um.
Preferably, the second-stage cyclone separator comprises a column section, a conical section and a ball section from top to bottom and is integrally connected (the arrangement and the principle of the second-stage cyclone separator are similar to those of the first-stage cyclone separator, but the second-stage cyclone separator is provided with the round ball section); the upper side end of the column section is also provided with a rotational flow inlet, the outer side of the column section is wound with an external refrigeration pipeline, an arc-shaped downward-inclined guide plate is also arranged between the rotational flow inlet and an internal overflow pipe, a central screen is also arranged in the column section, but the shape of the central screen is not completely the same as that of the central screen in the first-stage rotational flow separator, and the top end of the column section is also provided with an overflow pipe outlet; the propeller blades are arranged in the conical section, namely at the bottom of the central screen, the propeller blades are provided with a plurality of impellers from top to bottom, and the ratio of the diameter of each impeller to the diameter of the column section is 0.25-0.65: 1, and the diameter is gradually increased from top to bottom; and the bottom of the ball section is provided with a rotational flow underflow port which is the same as the rotational flow underflow port at the bottom of the same-stage rotational flow separator.
The high-salinity water treatment process based on cyclone reinforcement is characterized by comprising the following steps of:
(1) The seawater is fed into a primary refrigerating device through a first delivery pump for precooling to obtain primarily-cooled seawater, the primary refrigerating device adopts heat exchange refrigeration, and a cold source is pure water ice crystals after a medium solution is removed;
(2) The primarily cooled seawater is continuously fed into a secondary refrigeration device, and an unsaturated saline solution containing fine and uniform ice crystal particles is obtained through secondary refrigeration, and at the moment, the concentration of the high saline solution does not reach the saturation degree, so that the crystal salt cannot be separated out; the secondary refrigerating device adopts the suspension crystallization of mechanical stirring and ultrasonic wave auxiliary refrigeration technology, controls the solid-liquid ratio and the grain size within the range suitable for the separation of the cyclone by controlling the stirring speed and the freezing temperature of the blades, so as to improve the refrigerating efficiency and control the grain size of ice crystals;
(3) Feeding the secondary refrigeration product into a primary cyclone separator by a third delivery pump for separation; in the first-stage cyclone separator, the ice crystal particles perform high-speed autorotation to remove high-salinity water in the salt cells; solid-liquid separation is completed under the action of centrifugal force, large-particle ice crystals and a small amount of high-salt water solution which are subjected to self-desorption are obtained from an outlet of the overflow pipe, and small-particle pure water ice crystals and high-salt water solution are obtained from a rotational flow underflow port;
(4) The underflow of the first-stage cyclone separator automatically flows into a medium removing sieve to remove high-salt water solution, pure water ice crystals enter an ice crystal storage barrel from an ice crystal port, and the high-salt water enters a third-stage refrigerating device under the action of a fourth conveying pump;
(5) The product obtained from the outlet of the overflow pipe of the first-stage cyclone separator is also fed into a third-stage refrigerating device, the third-stage refrigerating device and the second-stage refrigerating device are arranged in the same way, under the action of the third-stage refrigerating device, the high-salt water solution forms ice crystal particles again, and the concentration of the residual solution is higher and higher due to continuous precipitation of pure water ice crystals, and after the saturation degree is reached, the saturated salt water begins to gradually precipitate the crystallized salt along with the continuous precipitation of the pure water ice crystals;
(6) Feeding the third-stage refrigeration product into a second-stage cyclone separator by a fourth delivery pump, separating and recovering ice crystals and crystallized salt particles, completing high-speed autorotation desorption of high-salinity water in the ice crystals and washing and purification of crystal salt attached to the surface under the action of a high centrifugal field, strong turbulence and high shear force in the second-stage cyclone separator, finally obtaining pure water ice crystals and saturated brine from an overflow outlet of the second-stage cyclone separator, and obtaining the crystal salt and the saturated brine from an underflow outlet;
(7) Feeding a product at an outlet of an overflow pipe of the secondary cyclone separator into a second medium removing sieve, and feeding pure water ice crystals obtained after medium solution is removed into an ice crystal storage barrel;
(8) Feeding a product of a rotational flow underflow port of the secondary rotational flow separator into a third medium removing sieve, removing a medium solution to obtain pure crystal salt, and placing the pure crystal salt in a crystal salt storage box;
(9) Mixing saturated brine under the screens of the medium removing screen II and the medium removing screen III, and feeding the mixture into the three-stage refrigeration device again for circulation;
(10) The pure water ice crystals are fed into a primary refrigerating device to serve as a cold source to pre-cool the seawater, the pure water ice crystals are melted into liquid fresh water which can be directly utilized after pre-cooling is completed, and the liquid fresh water enters a fresh water storage tank through a freezing outlet of an ice crystal storage barrel.
Preferably, the pressure of the cyclone inlet of the primary cyclone separator is set to be 0.14-0.2 mpa.
Preferably, the external refrigeration pipeline of the secondary cyclone separator keeps the internal temperature below 2 ℃.
Compared with the prior art, the invention has the advantages that:
the cyclone separator is adopted in the process, the density difference exists among the ice crystals, the solution and the crystal salt, the necessary condition of density separation is met, the centrifugal force generated by the cyclone field can reach dozens of times or even hundreds of times of the gravity, and the rapid separation and recovery of the ice crystal particles and the crystal salt can be realized. The seawater after suspension crystallization and ultrasonic-assisted freezing still maintains a certain solid-liquid ratio, meets the medium condition of cyclone separation, and effectively controlled fine ice crystal particles and crystallized salt particles also create favorable conditions for separation, in the cyclone separation process, as the density of the ice crystal particles is less than the medium density, and the density of the crystallized salt particles is greater than the medium density, pure water ice crystals and concentrated saturated brine can be obtained from an overflow pipe of the cyclone after separation, crystallized salt and saturated brine are obtained from bottom flow, and pure water ice crystals and crystallized salt can be obtained after further solid-liquid dehydration;
the process disclosed by the invention has the advantages of high desalting efficiency, simple flow, small occupied area, low energy consumption, no pollution, environmental friendliness, efficient recovery of fresh water resources and realization of preparation of crystallized salt, and is particularly suitable for large-scale application on ocean-going offshore platforms or offshore cities.
Drawings
FIG. 1 is a system architecture and flow diagram of the present invention;
FIG. 2 is a block diagram of the primary refrigeration unit of the present invention;
FIG. 3 is a block diagram of the secondary refrigeration unit of the present invention;
FIG. 4 is a block diagram of a primary cyclone separator of the present invention;
FIG. 5 is a functional schematic of the primary cyclone separator of the present invention;
FIG. 6 is a block diagram of a two-stage cyclone separator of the present invention;
FIG. 7 is a functional schematic of the two stage cyclonic separator of the present invention.
In the figure, 1-seawater storage tank, 2-conveying pipe, 3-second conveying pump, 4-fresh water storage tank, 5-first conveying pump, 6-first stage refrigerating device, 7-second stage refrigerating device, 8-ultrasonic auxiliary refrigerating device, 9-first stage cyclone separator, 10-third conveying pump, 11-crystallized salt storage tank, 12-third number medium removing sieve, 13-second stage cyclone separator, 14-external refrigerating pipeline, 15-fifth conveying pump, 16-third stage refrigerating device, 17-fourth conveying pump, 18-second number medium removing sieve, 19-first number medium removing sieve, 20-ice crystal storage barrel, 21-ice crystal opening, 22-freezing outlet, 23-feeding opening, 24-discharging opening, 25-refrigerating gas pipeline, 26-large paddle, 27-small paddle, 28-cyclone inlet, 29-deflector, 30-central screen, 31-sieve mesh, 32-cyclone overflow pipe, 33-cyclone flow opening, 34-column section, 35-cone section, 36-ball section, 37-spiral paddle section.
Detailed Description
The drawings are for illustration only; the terms "center," "upper," "lower," "rear," "vertical," "horizontal," "top," "inner," "outer," and the like are used in the orientation or positional relationship indicated in the drawings for convenience in describing the invention and for simplicity in description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed in a particular orientation, and be operated in a particular orientation, and are therefore not to be construed as limiting the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated.
Examples
As shown in fig. 1, a high brine treatment process based on cyclone reinforcement, which adopts the high brine treatment system based on cyclone reinforcement of the invention, is characterized by comprising the following specific steps:
(1) Seawater firstly enters the seawater storage tank 1 and is fed into the primary refrigerating device 6 for precooling at the flow rate of 200t/h through the first delivery pump 5, so that primarily-cooled seawater is obtained. As shown in fig. 2, the primary refrigerating device 6 adopts heat exchange refrigeration, and comprises an ice crystal storage barrel 20 for placing fresh water ice crystals, the outer side of the ice crystal storage barrel 20 is sequentially wound with a plurality of circles of conveying pipes 2 for conveying seawater from top to bottom, the top end of the ice crystal storage barrel is provided with an ice crystal port 21, the bottom of the lower side is provided with a freezing outlet 22, and the cold source is pure water ice crystals after removing the medium solution. The seawater in the delivery pipe 2 is fully subjected to heat exchange with the fresh water ice crystals in the ice crystal storage barrel 20, the seawater is cooled to 7 ℃, the fresh water ice crystals are melted at the same time, the melted fresh water ice crystals are high-purity fresh water, a pressure valve is arranged at a freezing outlet 22, the melted fresh water is controlled or closed to enter the fresh water storage tank 4, and the volume of the melted liquid is guaranteed to be kept two thirds of the volume of the ice crystal storage barrel 20.
(2) The primarily cooled seawater continues to be fed into the secondary refrigeration device 7. As shown in fig. 3, the secondary refrigeration device 7 comprises a freezing chamber, wherein a feed inlet 23 is arranged at the upper side of one end of the freezing chamber, a discharge outlet 24 is arranged at the lower side of the other end of the freezing chamber, and cooling gas pipelines 25 which are closely arranged in an s shape are arranged around the freezing chamber, and freezing gas with the temperature of-90 ℃ is circularly introduced into the freezing chamber at the flow rate of 20 t/h; the inside in freezing chamber sets up stirring paddle, stirring paddle includes big paddle 26 of several and little paddle 27 to be the crisscross arrangement, set up quantity according to the size in freezing chamber. An ultrasonic auxiliary refrigeration instrument 8 is arranged outside the freezing cavity to improve the phase change temperature of liquid drops, ultrasonic waves are uniformly and densely surrounded around the freezing cavity, and the temperature is kept within the range of-10 to-7 ℃.
The stirring blades are arranged in a large-small-large-small crossed mode, the stirring speed of the large blades 26 is 200 r/min, and the large blades rotate anticlockwise so as to control the flow of two-phase fluid; the stirring speed of the small blade 27 is 50 r/min and the small blade rotates clockwise to prevent ice crystals from being retained due to the fact that the ice crystals are close to the side wall of the freezing cavity. The ultrasonic auxiliary refrigerating instrument 8 emits low-frequency high-intensity ultrasonic waves with the frequency of 20000 HZ and the intensity of 800W to accelerate the freezing process and increase the treatment capacity, under the frequency, the seawater completes secondary refrigeration in about 15s and is discharged by a discharge pipe, at the moment, the temperature of the seawater is reduced to 0 ℃, the seawater is in a solid-liquid coexisting state, ice crystals with the average particle size of 500 um are suspended in the primarily concentrated seawater, and the solid-liquid ratio is controlled to be 1: about 3. The ice water two-phase fluid with uniform ice crystal size and controlled ice crystal content is more beneficial to being pumped into a first-stage cyclone separator 9 to enter the next step of separation.
(3) The product of the secondary refrigeration is fed by a third feed pump 10 at a pressure of 0.18mpa to the primary cyclone 9 for separation. As shown in fig. 4 and 5, a cyclone inlet 28 is provided at the upper end of the first-stage cyclone separator 9, an overflow pipe is provided at the center of the upper side, an arc-shaped downward-inclined guide plate 29 is provided between the cyclone inlet 28 and the overflow pipe, an overflow pipe outlet 32 is provided at the top end of the first-stage cyclone separator 9, a cyclone underflow port 33 is provided at the bottom end thereof, and a central screen 30 is further provided inside the overflow pipe; the central screen 30 is disposed next to the cyclone inlet 28, and the uppermost end thereof is fixedly connected to the inner wall of the casing of the first-stage cyclone separator 9, and is tapered, cylindrical, and conical downward, and is always spaced from the inner wall of the casing of the first-stage cyclone separator 9 by a certain distance.
The mesh number set on the central screen 30 is 325 meshes (i.e. the size of the screen hole 31 is 44 um), and the third transfer pump 10 is a slurry pump. In the conventional cyclone separator, because of the effect of the cyclone flow field, particles with smaller density and particle size are produced from the outlet 32 of the overflow pipe, particles with large density and coarse particles sink into the cyclone underflow port 33, but in the process of crushing and sorting ice, the density of ice is always smaller than that of water, after ice suspension is pumped into the primary cyclone separator 9 by a slurry pump, ice crystals easily float upwards and are blocked by the wall of the overflow pipe and are difficult to enter the central flow field, so a guide plate 29 is arranged between the cyclone inlet 28 and the overflow pipe, the inlet pressure is set to be 0.18mpa, and under the inlet pressure, the ice suspension can reach the central screen 30 with higher efficiency to be sorted.
Under the action of a high centrifugal force field, strong turbulence and high shear force in the primary cyclone separator 9, larger particle ice crystals (the maximum particle size is about 200 um) generated by the secondary refrigeration equipment 7 are primarily crushed, wherein fine particles enter the lower part of the central screen 30 through the screen holes 31 and are discharged along with the cyclone underflow ports 33, and because the particles are extremely fine (far smaller than 44 um), the phenomenon of wrapping salt cells does not exist, the particles can be directly sent into the first de-medium screen 19, pure ice crystals are obtained after separation, the larger particles cannot enter the lower part of the screen holes 30 due to the blocking of the screen holes 31, are output from the outlet 32 of the overflow pipe under the action of the flow field force and are sent into the third-stage refrigeration device 16, and the cyclone underflow ports obtain pure water ice crystals and high salt water solution of small particles.
(4) The underflow of the first-stage cyclone separator 9 automatically flows into a medium removing sieve 19 to remove the high-salt water solution, pure water ice crystals enter an ice crystal storage barrel 20 from an ice crystal opening, and the high-salt water enters a third-stage refrigerating device 16 under the action of a fourth delivery pump 17.
(5) The product obtained from the outlet 32 of the overflow pipe of the first-stage cyclone separator 9 is also fed into a third-stage refrigerating device 16, the third-stage refrigerating device 16 has the same arrangement and action with the second-stage refrigerating device 7, under the action of the third-stage refrigerating device 16, the high-salt water solution forms ice crystal particles with the maximum particle size of about 200 um again, and the concentration of the residual solution is higher and higher due to continuous precipitation of pure water ice crystals, after the saturation degree is reached, the saturated salt water begins to gradually precipitate crystal salt along with the continuous precipitation of the pure water ice crystals, and about 35g of salt is crystallized and precipitated per 1000g of water crystals.
(6) The product after the tertiary refrigeration is fed into a secondary cyclone separator 13 by a fourth delivery pump 17 at the pressure of 0.18mpa, and the ice crystals and the crystallized salt particles are separated and recovered. As shown in fig. 6 and 7, the second-stage cyclone separator 13 is similar to the first-stage cyclone separator 9 in arrangement and principle, and comprises a column section 34, a conical section 35 and a ball section 36 from top to bottom, and is integrally connected; the upper end of the column section 34 is also provided with a cyclone inlet, the outer side of the cyclone inlet is wound with the external refrigeration pipeline 14, the inner part of the cyclone inlet is also provided with a central screen, but the cyclone inlet is not completely the same as the central screen in the first-stage cyclone separator 9, the cyclone inlet is shorter than the central screen, the cyclone inlet is only arranged on the column section 34, and an overflow pipe and a guide plate are also arranged at the same position. The inside of conic section 35, central screen cloth bottom installation propeller blade 37 promptly, propeller blade 37 from the top down sets up a plurality of impellers, and the ratio of upside impeller diameter and column section 34 diameter is 0.25:1, the ratio of the diameter of the impeller at the lower side to the diameter of the column section 34 is 0.65:1; a swirl underflow port is also provided at the bottom of the ball segment 36.
After the tertiary refrigeration, the seawater solution is further concentrated, and after the suspension is introduced into the secondary cyclone separator 13, large-particle ice crystals are further sheared and crushed, salt wrapped in the ice crystals enters the seawater under the action of a flow field force, the mass fraction of the salt in the seawater is further increased, the temperature in the secondary cyclone separator 13 is kept below 2 ℃ through the external refrigeration pipeline 14, at the moment, salt is continuously crystallized and separated out in the secondary cyclone separator, the ice crystals are difficult to enter the position below the central screen under the blocking of the central screen, the salt crystals can smoothly pass through, and the primary separation is completed. Under the action of the impeller, the tangential speed of an internal flow field is increased, salt crystallization is accelerated to separate from the surface of the ice crystals, and secondary separation is completed. After the two-phase liquid enters the spherical section 36, the spherical structure strengthens the circulating flow in the flow field, so that the two-phase liquid circularly flows along the spherical wall, the larger the volume is, the larger the buoyancy force is, the smaller the density is, the ice crystals upwards return to the screen along the spherical wall and flow out along the overflow pipe, the salt crystals with the larger density and the smaller volume sink into the cyclone underflow port, finally, pure water ice crystals and saturated brine are obtained from the overflow pipe outlet of the secondary cyclone separator, and the crystallized salt and the saturated brine are obtained from the cyclone underflow outlet.
(7) And feeding a product at an outlet of an overflow pipe of the secondary cyclone separator 13 into a second medium removing sieve 18, and feeding pure water ice crystals obtained after medium solution is removed into an ice crystal storage barrel 20.
(8) And feeding a product at the cyclone underflow outlet of the second-stage cyclone separator 13 into a third medium removing sieve 12, removing a medium solution to obtain pure crystal salt, and placing the crystal salt in a crystal salt storage box 11.
(9) And mixing the saturated brine under the screens of the medium removing screen 18 and the medium removing screen 12, and feeding the mixture into the three-stage refrigeration device 16 again for circulation.
(10) The pure water ice crystals are fed into the primary refrigerating device 6 to be used as a cold source to pre-cool the seawater, and after the pre-cooling is completed, the pure water ice crystals are melted into liquid fresh water which can be directly utilized and enter the fresh water storage tank 4 through the freezing outlet 22 of the ice crystal storage barrel 20.
According to the invention, about 200t fresh water and 8.75 t crystallized salt can be obtained by passing 1000t of seawater through the system, and the salt content of the fresh water after cyclone separation is only 40 mg/l. The invention omits a heating step to melt pure water ice crystals, the melting latent heat of the ice at normal pressure is 334 kJ/kg and is far lower than the vaporization latent heat of water 2259.4 kJ/kg, and the invention is matched with a primary refrigerating device for use, thereby effectively reducing the power consumption on an offshore platform with limited resources.
The processing capacity of a certain coastal urban power plant distillation desalination project is about 20 million t/d, the invention can achieve the processing capacity of 24 million t/d by only about 70 sets of systems for parallel processing, and the floor area is about 7500 square meters.
The principle of the invention is as follows:
(1) Grain control is one of the keys to reducing "salt cell" formation. Heat conduction and heat convection are still the main ways of sea water desalination, temperature reduction and ice making by a freezing method, when the supercooling degree of the solution is too small during freezing, the ice forming efficiency is low and the ice forming time is long, and although the supercooling degree is increased, the ice forming time is reduced, the solute carried by the ice crystals is more due to the rapid growth of the ice crystal particles. Therefore, in order to improve the ice forming efficiency and control the size of ice crystal particles, the patent adopts a unique method combining suspension crystallization and ultrasonic-assisted freezing technology. During ultrasonic-assisted freezing, ultrasonic waves can cause cavitation bubbles to be generated in seawater, and the cavitation bubbles can serve as heterogeneous nucleation seeds, so that a large number of crystallization centers are formed in the liquid, and the formation of primary ice crystals is facilitated and accelerated. The cavitation bubbles which are continuously and rapidly expanded and broken can also generate strong supercooling degree to provide power for the formation of the ice crystals. Meanwhile, shock waves and micro-jets generated in the solution when cavitation bubbles are broken can generate strong impact action on ice crystal particles to limit the aggregation of the ice crystal particles, so that the size of the ice crystal particles in the seawater freezing process is effectively controlled, and the generation of 'salt cells' is further reduced.
(2) And removing internal salt cells and external salt by cyclone autorotation desorption of the ice crystal particles. The crystal salt ice is subjected to shearing and crushing and autorotation reinforced desorption treatment by adopting a supergravity rotational flow technology, and under the action of a high-speed rotational flow centrifugal force field, ice crystal particles revolve around the center of equipment along with fluid and simultaneously perform ultrahigh-speed autorotation. The ice body can be further broken by the high shearing force formed in the high-speed rotational flow field, and the salt cells in the ice crystal particles are dissected, so that the high-salinity water enclosed in the salt cells is separated from the ice crystal body. The high-speed autorotation motion formed by the rotational flow can enable the high-salt water in the ice crystal gaps to overcome the surface tension and the viscous adhesive force of the ice crystals and the capillary resistance in the pore channels, so that the high-salt water in the surfaces and the pore channels can be efficiently and slowly removed, and the aim of desalting and separating the ice crystals is fulfilled. The strong turbulence and high shear forces created in the swirling field wash the salt attached to the ice crystal surface.
(3) The separation of pure water ice crystals and crystal salt is realized by supergravity cyclone separation. Because the density difference exists among the ice crystal, the solution and the crystallized salt, the necessary condition of density sorting is met. The centrifugal force generated by the rotational flow field can reach dozens of times or even hundreds of times of the gravity, and the ice crystal particles and the crystallized salt can be quickly separated and recovered. The seawater after suspension crystallization and ultrasonic-assisted freezing still maintains a certain solid-liquid ratio to meet the medium condition of cyclone separation, and effectively controlled fine ice crystal particles and crystallized salt particles create favorable conditions for separation. In the cyclone separation process, because the density of ice crystal particles is less than the density of a medium, and the density of crystallized salt particles is greater than the density of the medium, pure water ice crystals and concentrated saturated brine can be obtained from an overflow pipe of the cyclone after separation, and crystallized salt and saturated brine are obtained from underflow. Further solid-liquid dehydration to obtain pure water ice crystals and crystallized salt.
Comparative example
The reverse osmosis desalination accounts for about 60 percent of the total amount of the actual seawater desalination, the treatment capacity is large, but the reverse osmosis desalination rate is lower. The Total Dissolved Solids (TDS) of seawater in a certain area is as high as 41000 mg/l-48000 mg/l, which belongs to clear high-salt seawater, a seawater reverse osmosis device is adopted in a certain factory in the certain area, a 4 x 600MW (net output) ultra-supercritical wet cooling unit is installed, the salt content of produced water is still as high as 410-480 mg/l according to the operation of the three-year desalination rate of 99.0%, the yield is 300t/h, and the yield is large but can not meet the requirements of the quality of fresh water. And fresh water reverse osmosis (BWRO) is continuously arranged after the seawater reverse osmosis device, and the produced water is used as fresh water.
If the distillation method is used, the average TDS after the treatment is 2.5mg/l, the purity of the obtained fresh water is high, but the treatment capacity of the distillation method is lower, and the treatment capacity is only 93.4t/h under the same scale. The purity of the desalted seawater obtained by the invention can reach 40mg/l, the desalted seawater meets the fresh water standard, the treatment capacity is large, the system treatment capacity with the same scale can reach 150t/h under the condition of a simple process, and the seawater desalting quality and the treatment capacity are both considered. Compared with a distillation method, the method saves about one sixth of system energy consumption.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, alterations, additions or substitutions within the spirit and scope of the present invention.
Claims (10)
1. A high-salinity water treatment system based on rotational flow strengthening comprises a seawater storage tank, a delivery pump, a refrigerating device, a fresh water storage tank and a crystallized salt storage tank, and is characterized by further comprising a rotational flow separator and a medium removing sieve; the seawater storage tank is connected with a first delivery pump through a delivery pipe and then connected with a primary refrigerating device through the delivery pipe; the first-stage refrigerating device is connected with the second-stage refrigerating device through a second conveying pump and a conveying pipe, and the second-stage refrigerating device is connected with the first-stage cyclone separator through a third conveying pump and a conveying pipe; the top end of the first-stage cyclone separator is connected with a third-stage refrigerating device through a fourth conveying pump and a conveying pipe, the bottom end of the first-stage cyclone separator is connected with a first medium removing sieve through the conveying pipe, a product at one end of the first medium removing sieve enters the first-stage refrigerating device, and a product at the other end of the first medium removing sieve enters the third-stage refrigerating device through the fourth conveying pump; the tertiary refrigerating plant is connected with a second-stage cyclone separator, the top end of the second-stage cyclone separator is connected with a second medium removing sieve through a conveying pipe and a fifth conveying pump, the bottom end of the second-stage cyclone separator is connected with a third medium removing sieve through a conveying pipe, a product at one end of the third medium removing sieve enters a crystallized salt storage box, a product at the other end of the third medium removing sieve returns to the tertiary refrigerating plant through a fourth conveying pump, the product at one end of the second medium removing sieve enters a first-stage refrigerating plant, and the product at the other end of the second medium removing sieve enters the tertiary refrigerating plant through the fourth conveying pump.
2. The high-salinity water treatment system based on cyclone reinforcement of claim 1, wherein the primary refrigeration device comprises an ice crystal storage barrel for holding fresh water ice crystals, the outer side of the ice crystal storage barrel is sequentially wound with a plurality of turns of conveying pipes for conveying seawater from top to bottom, the top end of the ice crystal storage barrel is provided with an ice crystal port, the bottom of the lower side of the ice crystal storage barrel is provided with a freezing outlet, seawater in the conveying pipes can be cooled to 6-8 ℃ by exchanging heat with the fresh water ice crystals in the ice crystal storage barrel, and the fresh water ice crystals are melted.
3. The high salinity water treatment system based on cyclone reinforcement of claim 2, wherein the product of the first medium removing sieve and the third medium removing sieve entering the first stage refrigeration device is fresh water ice crystals, and is directly placed in the ice crystal storage barrel through an ice crystal port.
4. The high-salinity water treatment system based on rotational flow strengthening according to claim 1, wherein the secondary refrigeration device comprises a freezing chamber, a feed inlet is arranged at the upper side of one end of the freezing chamber, a discharge outlet is arranged at the lower side of the other end of the freezing chamber, and s-shaped and closely arranged refrigeration gas pipelines are arranged around the freezing chamber; stirring blades are arranged in the freezing cavity, comprise a plurality of large blades and small blades and are arranged in a crossed manner; an ultrasonic auxiliary refrigeration instrument is arranged outside the freezing cavity to improve the phase change temperature of liquid drops, ultrasonic waves are uniformly and densely surrounded around the freezing cavity, and the temperature is kept within the range of-10 to-7 ℃.
5. The high salinity water treatment system based on whirl-strengthening of claim 4, wherein the stirring speed of the big paddle is 200 r/min and rotates counterclockwise to control the flow of two-phase fluid; the stirring speed of the small blades is 50 r/min and the small blades rotate clockwise so as to prevent ice crystals from approaching the side wall of the freezing cavity to cause ice crystal retention; the ultrasonic auxiliary refrigeration instrument emits low-frequency high-intensity ultrasonic waves with the frequency of 20000 HZ and the intensity of 800W.
6. The high salinity water treatment system based on cyclone reinforcement of claim 1, wherein the upper side end of the primary cyclone separator is provided with a cyclone inlet, the center of the inside of the upper side is provided with an overflow pipe, an arc-shaped downward-inclined guide plate is arranged between the cyclone inlet and the overflow pipe, the outlet of the overflow pipe is arranged at the top end of the primary cyclone separator, the bottom end of the overflow pipe is provided with a cyclone underflow port, and the inside of the overflow pipe is also provided with a central screen; the central screen mesh is provided with screen holes with the size of 40 +/-5 um.
7. The high salinity water treatment system based on cyclone reinforcement of claim 1, wherein, the secondary cyclone separator comprises a column section, a cone section and a ball section from top to bottom and is integrally connected; an arc-shaped downward-inclined guide plate is also arranged between the rotational flow inlet and the overflow pipe, an external refrigeration pipeline is wound on the outer side of the column section, and a central screen is arranged inside the column section; the propeller blades are arranged in the conical section, namely at the bottom of the central screen, the propeller blades are provided with a plurality of impellers from top to bottom, and the ratio of the diameter of each impeller to the diameter of the column section is 0.25-0.65: 1, and the diameter is gradually increased from top to bottom; and the bottom of the ball section is provided with a rotational flow underflow port.
8. A high-salinity water treatment process based on cyclone reinforcement, which adopts the system of any one of claims 1 to 7, and is characterized by comprising the following specific steps:
(1) Feeding the seawater into a primary refrigerating device for precooling to obtain primarily cooled seawater;
(2) The primarily cooled seawater is continuously fed into a secondary refrigerating device to obtain unsaturated saline solution containing fine and uniform ice crystal particles;
(3) Feeding the secondary refrigeration product into a primary cyclone separator, and performing high-speed autorotation on ice crystal particles under the action of the primary cyclone separator to remove high-salinity water in the salt cells;
(4) Enabling the underflow of the first-stage cyclone separator to flow into a first medium removing sieve to remove high-salt water solution, enabling pure water ice crystals to enter an ice crystal storage barrel, and enabling high-salt water to enter a third-stage refrigerating device;
(5) Products obtained from an outlet of an overflow pipe of the first-stage cyclone separator are also fed into the third-stage refrigerating device, and under the action of the third-stage refrigerating device, the saturated brine begins to gradually separate out crystallized salt;
(6) Feeding the tertiary refrigeration product into a secondary cyclone separator for separating and recovering ice crystals and crystallized salt particles;
(7) Feeding pure water ice crystals and saturated brine obtained from an outlet of an overflow pipe of the secondary cyclone separator into a second medium removing sieve, and removing the medium solution to obtain pure water ice crystals;
(8) Feeding the crystallized salt and saturated brine obtained from the cyclone underflow port of the secondary cyclone into a third medium removing sieve, and removing the medium solution to obtain pure crystallized salt;
(9) Mixing saturated brine under the screens of the medium removing screen II and the medium removing screen III, and feeding the mixture into the three-stage refrigeration device again for circulation;
(10) Pure water ice crystals are fed into a primary refrigerating device to be used as a cold source to pre-cool the seawater.
9. The high salinity water treatment process based on cyclone reinforcement of claim 8, wherein the pressure of the cyclone inlet of the primary cyclone separator is set to be 0.14-0.2 mpa.
10. The high salinity water treatment process based on cyclone reinforcement of claim 8, wherein, the external refrigeration pipeline of the secondary cyclone separator keeps the internal temperature below 2 ℃.
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