CN113666444A - Binary system evaporative crystallization device and evaporative crystallization method - Google Patents
Binary system evaporative crystallization device and evaporative crystallization method Download PDFInfo
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- CN113666444A CN113666444A CN202110907104.0A CN202110907104A CN113666444A CN 113666444 A CN113666444 A CN 113666444A CN 202110907104 A CN202110907104 A CN 202110907104A CN 113666444 A CN113666444 A CN 113666444A
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- 238000002425 crystallisation Methods 0.000 title claims abstract description 69
- 230000008025 crystallization Effects 0.000 title claims abstract description 57
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- 238000001704 evaporation Methods 0.000 claims abstract description 66
- 230000008020 evaporation Effects 0.000 claims abstract description 61
- 238000009833 condensation Methods 0.000 claims abstract description 51
- 230000005494 condensation Effects 0.000 claims abstract description 51
- 239000002699 waste material Substances 0.000 claims abstract description 32
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- 238000000034 method Methods 0.000 claims abstract description 9
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- 238000005057 refrigeration Methods 0.000 claims abstract description 7
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- 230000009977 dual effect Effects 0.000 claims 9
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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
- C02F1/048—Purification of waste water by evaporation
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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
Abstract
The invention discloses a binary system evaporative crystallization device and an evaporative crystallization method, and belongs to the technical field of evaporative crystallization. The device mainly comprises a concentration tower, a condensation tower group, a crystallization evaporation kettle and a circulation liquid circulation pipeline of the concentration tower, wherein the method preheats and heats pumped waste liquid to be treated and unsaturated concentrated liquid which are used as spray liquid of the concentration tower to enter the concentration tower, and circulating air and the waste liquid are in countercurrent contact in the tower to convert heat and moisture to realize concentration; the condensate obtained after treatment is sent to other condensing towers to be used as spraying liquid for recycling after heat exchange and refrigeration; boiling and evaporating the saturated concentrated solution in an evaporation crystallization kettle under a slight negative pressure to obtain salt crystals. The device and the invention use the surface evaporation principle to concentrate the waste liquid to a saturated state, then use the micro-negative pressure boiling evaporation crystallization principle, and the secondary steam generated by crystallization is recycled to the surface evaporation section by using the steam jet pump, thereby realizing the secondary utilization of heat energy, achieving the purpose of saving energy and simultaneously solving the problems existing in the use process of the traditional evaporator.
Description
Technical Field
The invention relates to an evaporative crystallization device and an evaporative crystallization method, in particular to a binary evaporative crystallization device and an evaporative crystallization method, belongs to the technical field of evaporative crystallization, and is particularly suitable for pretreatment and reduction of waste liquid containing high-concentration organic matters and inorganic matters and complex industrial wastewater.
Background
In the process of crystallizing liquid containing high salt and high organic matters, an MVR evaporator or a triple-effect evaporator is usually adopted, the two evaporators are both used for evaporating by utilizing the principle that waste liquid is heated to the boiling point under negative pressure and then water in the waste liquid is generated into water vapor through boiling, and the evaporator is widely applied to the salt chemical industry. However, in the complex process of treating industrial waste liquid, because the liquid has high hardness and a large amount of COD, acid, alkali and other substances exist, crystallization is very difficult, and various conditions such as easy corrosion, easy blockage, coking and the like are very common, so that after equipment is constructed and put into operation, continuous and stable operation cannot be realized, and certain economic loss and great troubles are caused to enterprises.
Disclosure of Invention
In order to solve the technical problems, the invention provides a binary system evaporative crystallization device and an evaporative crystallization method, evaporative crystallization carried out by using the device can concentrate waste liquid to a saturated state by utilizing a surface evaporation principle, then heat and crystallize by utilizing a micro negative pressure boiling evaporation mode, and secondary steam generated by crystallization returns to a surface evaporation section for secondary utilization, so that the purpose of energy conservation is achieved, and the problems existing in the use process of the traditional evaporator are solved.
The technical scheme of the invention is as follows:
the invention discloses a binary system evaporative crystallization method, which mainly comprises the following steps:
waste liquid is pumped into a circulating liquid circulating pipeline of the concentration tower, preheated, heated and heated, and then enters the concentration tower from the top of the concentration tower, circulating air enters the concentration tower from the bottom of the concentration tower and is in countercurrent contact with the waste liquid, and moisture in the waste liquid is transferred to the air to realize concentration;
saturated high-temperature humid air formed at the top of the condensing tower sequentially enters each condensing tower in the condensing tower group from the bottom of the condensing tower group for condensation, and the formed condensed water is subjected to heat exchange and refrigeration and then is used as spray water of other condensing towers for spraying into the condensing tower; introducing the air subjected to condensation treatment into the bottom of the concentration tower as the circulating air;
discharging the obtained unsaturated concentrated solution into a circulating solution circulating pipeline of a concentration tower to be combined with the pumped waste liquid;
and discharging the obtained saturated concentrated solution into an evaporation crystallization kettle at regular time for micro negative pressure boiling evaporation, discharging the mixture obtained after evaporation into centrifugal equipment for solid-liquid separation to obtain salt crystals.
The further technical scheme is as follows:
the circulating liquid circulating pipeline of the concentration tower comprises a high-temperature condensed water preheating heat exchanger and a steam heater which are sequentially communicated along the flowing direction of unsaturated condensed water, the unsaturated condensed water discharged from the bottom of the concentration tower enters the high-temperature condensed water preheating heat exchanger as a cold side, and one path of high-temperature condensed water formed by the condensation tower enters the high-temperature condensed water preheating heat exchanger as a hot side, so that the preheating of the unsaturated condensed water and the refrigeration of the high-temperature condensed water are realized; the preheated unsaturated concentrated solution enters a steam heater as a cold side, secondary steam obtained by the micro-negative pressure boiling evaporation of the evaporation crystallization kettle is injected by a steam jet pump to be pressurized and heated up and then enters the steam heater as a hot side, and the temperature of the circulating unsaturated concentrated solution can be raised to 80-85 ℃.
The further technical scheme is as follows:
evaporating the saturated concentrated solution in the evaporation crystallization kettle to 30-40% of solid content under the condition of micro-negative pressure boiling evaporation, and discharging the saturated concentrated solution to an external centrifugal device for solid-liquid separation to obtain salt crystals; the mother liquid is returned to the evaporation crystallization kettle for circulation and crystallization or is discharged out of the evaporation crystallization system.
The further technical scheme is as follows:
a liquid level sensor and a density sensor are positioned at the bottom in the concentration tower, and when the density of the liquid at the bottom of the concentration tower reaches a preset value, the concentration tower is controlled to discharge saturated concentrated liquid into the evaporation crystallization kettle; and when the density of the liquid at the bottom of the concentrated solution does not reach a preset value but reaches a preset minimum working liquid level, controlling the concentration tower to discharge unsaturated concentrated solution into the circulating liquid circulating pipeline of the concentration tower.
The invention also discloses a double-system evaporative crystallization device applied to the method, which comprises a concentration tower, wherein an unsaturated concentrated solution outlet at the bottom of the concentration tower is communicated with the top of the concentration tower through a circulating solution circulating pipeline of the concentration tower; a saturated concentrated solution outlet at the bottom of the concentration tower is communicated with a crystallization evaporation kettle through a pipeline; a gas outlet of the concentration tower at the top of the concentration tower is communicated with a condensed gas inlet at the bottom of a condensation tower set through a pipeline;
the condensation tower group comprises at least two condensation towers, and a condensate outlet at the bottom of each condensation tower is communicated with the tops of other condensation towers after passing through a pipeline and a heat exchange device; and a condensed gas outlet of the previous condensing tower in the condensing tower group is communicated with a condensed gas inlet of the next condensing tower through a pipeline, and a condensed gas outlet of the condensing tower at the tail end is communicated with a gas inlet of the concentrating tower through a pipeline to form an air circulation loop.
The further technical scheme is as follows:
the circulating liquid circulating pipeline of the concentration tower comprises a high-temperature condensed water preheating heat exchanger and a steam heater which are sequentially communicated along the flowing direction of unsaturated condensed liquid, an unsaturated condensed liquid discharge port is communicated with a cold side inlet of the high-temperature condensed water preheating heat exchanger through a pipeline and an evaporation tower circulating pump, a cold side outlet of the high-temperature condensed water preheating heat exchanger is communicated with a cold side inlet of the steam heater through a pipeline, and a cold side outlet of the steam heater is communicated with the top of the concentration tower through a pipeline.
The further technical scheme is as follows:
and a cold side inlet of the high-temperature condensed water preheating heat exchanger is communicated with a waste liquid source to be treated through a pipeline and a water inlet pump.
The further technical scheme is as follows:
the condensation tower group comprises a first condensation tower and a second condensation tower, wherein a condensate outlet at the bottom of the first condensation tower is communicated with a hot side pipeline inlet of the high-temperature condensate preheating heat exchanger after passing through a pipeline and a high-temperature condensate circulating pump, and an outlet of the hot side pipeline is communicated with the top of the second condensation tower through a pipeline; and a condensate outlet at the bottom of the second condensing tower is communicated with a hot side pipeline inlet of a cooling plate type heat exchanger after passing through a pipeline and a low-temperature condensate circulating pump, and an outlet of the hot side pipeline is communicated with the top of the first condensing tower.
The further technical scheme is as follows:
a cold side inlet and a cold side outlet of the cooling plate type heat exchanger are respectively communicated with an external cooling circulating water supply pipeline and a water return pipeline; and water distributors for spraying liquid are positioned at the tops of the concentration tower, the first condensation tower and the second condensation tower.
The further technical scheme is as follows:
a secondary steam outlet of the crystallization evaporation kettle is communicated with an injection interface of a steam jet pump through a pipeline, and an outlet of the steam jet pump is communicated with a hot side inlet of the steam heater; and the middle sections of the condensing towers in the condensing tower and the condensing tower group are provided with folded plate type structured packing in a positioning manner.
The beneficial technical effects of the invention are as follows:
the method utilizes the difference of saturated moisture contents of the circulating gas at different temperatures to concentrate the waste liquid containing high salt and high organic matters, and utilizes the surface evaporation principle, namely, the moisture in the raw material is extracted by utilizing the moisture carrying capacity of air, so as to achieve the purpose of concentration; at least two condensing towers are used in the subsequent concentration, and micro-positive pressure is adopted by combining the condensing towers, so that heat exchangers in various forms such as plate heat exchangers can be adopted, the frequency of blockage and scaling in the heat exchangers is reduced through high flow rate, and the stable operation of the equipment can be ensured;
the invention adopts a micro-negative pressure boiling evaporation mode to evaporate and crystallize the concentrated waste liquid, the generated high-temperature secondary steam is injected and pressurized by a steam injection pump to heat the waste liquid and the circulating liquid, and the system also utilizes the high-temperature condensate generated by the condensing tower group to be used as spray water at the tops of other condensing towers in the condensing tower group after heat exchange and cooling, thereby realizing the cyclic utilization of materials and energy and achieving the purpose of energy conservation.
The use of the steam jet pump not only enables the high-temperature secondary steam to be pressurized and heated, and be recycled by 100 percent and efficiently used for heating the circulating liquid of the surface evaporation equipment, but also enables a heat exchange component not to bear negative pressure, thereby being capable of using an economic and efficient plate heat exchanger, and on the other hand, the steam jet pump also replaces a water ring vacuum pump or a water jet vacuum pump, reduces the power consumption of a system, and achieves the purpose of energy conservation.
Drawings
FIG. 1 is a schematic view of the overall structure of the apparatus of the present invention; wherein the dotted line represents the circulating air flow path;
wherein:
1. a water inlet pump;
2. an evaporation tower circulating pump;
3. preheating a heat exchanger by high-temperature condensed water;
4. a concentration tower; 41. an unsaturated concentrated solution outlet; 42. a saturated concentrated solution outlet; 43. a gas outlet of the concentration tower;
5. folded plate type packing;
6. a water distributor;
7. a condensing tower set; 71. a first condensing tower; 72. a second condensing tower;
8. a circulating liquid circulating pipeline of the concentration tower;
9. a concentration discharge pump;
10. a steam heater;
11. a high-temperature condensed water circulating pump;
12. a low-temperature condensed water circulating pump;
13. cooling the plate heat exchanger;
14. a crystallization evaporation kettle;
15. a steam jet pump;
16. and a circulating fan.
Detailed Description
In order to make the technical means of the present invention clearer and to make the technical means of the present invention capable of being implemented according to the content of the specification, the following detailed description of the embodiments of the present invention is made with reference to the accompanying drawings and examples, which are provided for illustrating the present invention and are not intended to limit the scope of the present invention.
The invention discloses a double-system evaporative crystallization device, which mainly comprises a concentration tower 4, a crystallization evaporation kettle 14, a condensation tower group 7, a concentration tower circulating liquid circulating pipeline 8 and a heat exchange device.
The lowest point of the bottom of the concentration tower 4 is provided with an unsaturated concentrated solution outlet 41, the unsaturated concentrated solution outlet 41 is communicated with the top of the concentration tower through a circulating liquid circulating pipeline 8 of the concentration tower, wherein the circulating liquid circulating pipeline 8 of the concentration tower comprises a high-temperature condensed water preheating heat exchanger 3 and a steam heater 10 which are sequentially communicated and arranged along the flowing direction of the unsaturated concentrated solution. The specific connection mode is that the unsaturated concentrated solution outlet 41 is communicated with the cold side inlet of the high-temperature condensed water preheating heat exchanger 3 through a pipeline and an evaporation tower circulating pump 2 positioned at the outlet, the cold side outlet of the high-temperature condensed water preheating heat exchanger 3 is communicated with the cold side inlet of the steam heater 10 through a pipeline, and the cold side outlet of the steam heater 10 is communicated with the top of the concentration tower 4 through a pipeline; in addition, a cold side inlet of the high-temperature condensed water preheating heat exchanger 3 is communicated with a waste liquid source to be treated through a pipeline and a water inlet pump 1. Thus, the unsaturated condensate and the waste liquid to be treated pass through the high-temperature condensate preheating heat exchanger 3 and the steam heater 10 in this order as the cold side, are heated to a predetermined temperature, and are sprayed from the top of the concentrating tower 4.
A saturated concentrated solution outlet 42 is arranged at the upper position of the bottom of the concentration tower 4, and the saturated concentrated solution outlet 42 is communicated with the crystallization evaporation kettle 14 through a pipeline. The bottom department location in the concentrated tower 4 is equipped with a level sensor and a density sensor, and the location is equipped with one row of concentrate pump 9 on the outside pipeline of saturated liquid discharge port of concentrated tower, after detecting that concentrate density reaches the default, row's concentrate pump starts, arranges the saturated concentrate to crystallization evaporation cauldron, and the liquid level height bottom this concentrated tower of control through level sensor.
The crystallization evaporation kettle 14 is a jacketed evaporation kettle or a semi-coil heating evaporation kettle, a steam inlet for an external steam source to enter and a condensate outlet for condensate water in the jacket or the coil to discharge are arranged at the upper part of the jacket or the outer coil of the evaporation kettle, raw steam enters the jacket or the coil from the steam inlet, exchanges heat with the evaporation kettle to form steam condensate water, and then is discharged from the condensate outlet. A secondary steam outlet is formed in the top cover of the evaporation kettle 14 and is communicated with an injection inlet of a steam jet pump 15 through a pipeline, a driving steam inlet of the steam jet pump is communicated with an external steam source through a pipeline, and an outlet of the steam jet pump 15 is communicated with a hot side inlet of the steam heater 10. The secondary steam generated by mixing is used as the hot side of the steam heater 10, the preheated circulating unsaturated concentrated solution and the waste liquid to be treated are used as the cold side of the steam heater 10, and the two are subjected to heat exchange in the steam heater 10. In addition, a stirring device is positioned in the crystallization evaporation kettle 14, and a crystallization salt outlet is arranged at the bottom of the kettle body.
The highest point of the top of the concentration tower 4 is provided with a concentration tower gas outlet 43, and the concentration tower gas outlet 43 is communicated with a condensed gas inlet at the bottom of the condensation tower group 7 through a pipeline. The condensing tower group 7 comprises at least two condensing towers, and a condensate outlet at the bottom of each condensing tower is communicated with the tops of other condensing towers after passing through a pipeline and a heat exchange device; and the condensed gas outlet of the previous condensing tower in the condensing tower group 7 is communicated with the condensed gas inlet of the next condensing tower through a pipeline, and the condensed gas outlet of the condensing tower at the tail end is communicated with the gas inlet of the condensing tower through a pipeline and a circulating fan 16 to form an air circulation loop.
In the present embodiment, the condensation tower group 7 includes two condensation towers, i.e., a first condensation tower 71 and a second condensation tower 72. The condensate outlet at the bottom of the first condensation tower 71 is communicated with the hot side pipeline inlet of the high-temperature condensate preheating heat exchanger 3 through a pipeline and a high-temperature condensate circulating pump 11, and the hot side pipeline outlet is communicated with the top of the second condensation tower through a pipeline, namely, the high-temperature condensate formed by condensation in the first condensation tower enters the high-temperature condensate preheating heat exchanger as the hot side. The condensate outlet of the bottom 72 of the second condensing tower is communicated with the hot side pipeline inlet of a cooling plate heat exchanger 13 through a pipeline and a low-temperature condensate circulating pump 12, and the outlet of the hot side pipeline is communicated with the top of the first condensing tower, wherein the cold side inlet and the cold side outlet of the cooling plate heat exchanger 13 are respectively communicated with an external cooling circulating water source, namely, the low-temperature condensate formed by condensation in the second condensing tower enters the cooling plate heat exchanger as the hot side. The condensed gas outlet at the top of the first condensing tower 71 is communicated with the condensed gas inlet at the bottom of the second condensing tower 72 through a pipeline, and the condensed gas outlet at the top of the second condensing tower 72 is communicated with the gas inlet at the bottom of the concentration tower through a pipeline and the circulating fan 16.
In this embodiment, a water distributor 6 for spraying liquid is positioned at the top of each of the concentration tower 4, the first condensation tower 71 and the second condensation tower 72, and the liquid entering the top of the tower through the pipeline is uniformly distributed from the top to the bottom of the tower through the water distributor.
In this embodiment, the folding plate type structured packing 5 is positioned at the middle position of each of the condensing towers 4 and 7, such as the first condensing tower 71 and the second condensing tower 72, and can increase the water-gas contact area and promote the conversion of gas phase and liquid phase.
In the embodiment, the corrosion-resistant polymer composite material is mainly used as the contact medium part and the equipment main body material of the concentration tower, the condensation tower and other main equipment, so that the corrosion resistance of the system can be obviously improved, the application of metal materials is reduced, and the equipment cost can be effectively reduced.
The invention also discloses a binary system evaporation crystallization method, which mainly comprises the following steps:
the waste liquid is pressurized by a water inlet pump 1 and sent to a circulating liquid circulating pipeline 8 of the concentration tower. The circulating liquid circulating pipeline 8 of the concentration tower mainly comprises an evaporation tower circulating pump 2, a high-temperature condensate preheating heat exchanger 3 and a steam heater 10 which are sequentially communicated along the flowing direction of unsaturated concentrated liquid and are used for circulating the unsaturated concentrated circulating liquid in the concentration tower.
The unsaturated concentrated circulating liquid flows out from an unsaturated concentrated liquid outlet at the bottom of the concentrating tower 4 and then enters a circulating liquid circulating pipeline 8 of the concentrating tower. The unsaturated concentrated circulating liquid is pressurized by a circulating pump 2 of the evaporation tower, is sent into a high-temperature condensed water preheating heat exchanger 3, is merged with the waste liquid and then is preheated by the high-temperature condensed water preheating heat exchanger 3 as a cold side, then enters a steam heater 10 through a pipeline to be heated by the steam heater 10 as the cold side, heats the temperature of the waste liquid and the unsaturated concentrated circulating liquid to 80-85 ℃ through the two heat exchange devices, and then is distributed to a concentration tower 4 through a water distributor 6 at the top in the concentration tower 4. The middle section position in the concentration tower 4 is provided with a folded plate type structured packing for increasing the contact area of air and water and promoting the transfer of water in the waste liquid to the gas phase. When the density of the liquid at the bottom of the concentration tower reaches a preset value, controlling a concentration discharge pump 9 to discharge saturated concentrated liquid into the evaporation crystallization kettle; and when the density of the liquid at the bottom of the concentrated solution does not reach a preset value but reaches a value above a preset minimum working liquid level, controlling the concentration tower to discharge unsaturated concentrated solution into the circulating liquid circulating pipeline of the concentration tower.
The circulating fan 16 continuously blows circulating air into the concentration tower 4 from the bottom of the concentration tower. In the tower, circulating air is in continuous countercurrent contact with high-temperature waste liquid, the waste liquid forms a liquid film on the surface of the folded plate, and after the liquid film is in contact with the air, moisture in the waste liquid is transferred to the air to form a concentration process. Saturated high-temperature wet air is formed when the air reaches the top of the concentration tower, and the saturated high-temperature wet air sequentially enters each condensation tower in the condensation tower group from the bottom of the condensation tower group 7 for condensation; the formed condensed water is subjected to heat exchange and refrigeration and then is used as spray water of other condensing towers to be sprayed into the condensing towers; the air after condensation treatment is used as circulating air and introduced into the bottom of the concentration tower.
The condensing tower group 7 comprises at least two condensing towers, in this embodiment, a first condensing tower 71 and a second condensing tower 72, and each condensing tower is provided with a water distributor 6 and a folded plate type packing 5. Saturated high-temperature humid air enters from the lower part of the first condensing tower and is fully contacted with condensed water at the folded plate type packing, the temperature of the moisture in the air is reduced when encountering the condensed water, the moisture in the air is converted from a gaseous state into a liquid state, and meanwhile, latent heat is released, so that the temperature of the condensed water is increased. The bottom of the first condensing tower is provided with a condensate outlet for being connected with a high-temperature condensate circulating pump 11, the high-temperature condensate passes through the high-temperature condensate circulating pump 11 and is conveyed to the high-temperature condensate preheating heat exchanger 3 to provide heat, and after the high-temperature condensate is subjected to heat exchange with the condensate circulating liquid of the condensing tower, the temperature of the condensate is reduced, the condensate is returned to the top of the second condensing tower 72, and the condensate is sprayed into the tower through a water distributor and then is contacted with the air.
Namely, the discharged unsaturated concentrated solution enters the high-temperature condensate preheating heat exchanger 3 as the cold side, and the high-temperature condensate formed by the first condensing tower enters the high-temperature condensate preheating heat exchanger 3 as the hot side, so that the preheating of the unsaturated concentrated solution and the refrigeration of the high-temperature condensate are realized; the preheated unsaturated concentrated solution enters a steam heater 10 as a cold side, secondary steam obtained by boiling and evaporating at a slight negative pressure of an evaporation crystallization kettle is pressurized and heated up and then enters the steam heater as a hot side, and the unsaturated concentrated solution can be heated up to 80-85 ℃.
The air cooled by the first condensing tower 71 has a higher temperature, generally reaching about 60 ℃, and in order to further recover moisture in the air, the air is continuously sent to the second condensing tower 72 through a pipeline, and the spray liquid at the top of the second condensing tower 72 is used for further cooling and dehumidifying. The structure of the second condensing tower is the same as that of the first-stage condensing tower, a bottom condensed water outlet, a low-temperature condensed water circulating pump 12 and a cooling plate type heat exchanger 13 form a circulating pipeline, outside cooling circulating water is used for cooling condensed water, the cooled condensed water is conveyed to the top of the first condensing tower and sprayed into the tower through a water distributor, latent heat of water condensation in the recovered air forms high-temperature condensed water and is conveyed to a high-temperature condensed water preheating heat exchanger 3.
The saturated concentrated solution discharged from the bottom of the concentration tower 4 is sent to an evaporation crystallization kettle 14 for boiling evaporation under a slight negative pressure. The evaporative crystallization kettle adopts a jacket type or an outer semi-coil type, external steam is introduced into the jacket or the coil, the external steam is used for heating up the concentrated solution in the kettle until boiling, water in the micro negative pressure boiling evaporation is converted into secondary steam, and then the secondary steam is sent to a steam jet pump 15 for repressurization and provides heat for a steam heater 10 for heating up the unsaturated concentrated solution. And (3) with the continuous reduction of the water in the evaporation crystallization kettle 14, finally reaching supersaturation, precipitating the crystallization salt, when the water is evaporated to 30-40% of solid content, sending the solution to an external centrifugal device for solid-liquid separation, and taking out the salt crystal from the system to obtain the salt crystal.
The principle of the invention is as follows:
the waste liquid to be treated is pumped to a circulating liquid circulating pipeline of the concentration tower by a water inlet pump, is heated by a high-temperature condensate preheating heat exchanger and a steam heater which are connected in series, and enters the concentration tower from the top of the concentration tower after being heated to a preset temperature; air blown by the circulating fan enters the concentration tower from the top of the concentration tower, the air and the air are in countercurrent contact in the tower, heat of circulating liquid is transferred to the air, and meanwhile, moisture in waste liquid is transferred to a gas phase, so that concentration is realized.
And (4) after the concentrated saturated liquid reaches the preset concentration, discharging the saturated liquid to a crystallization kettle at regular time. Raw steam is introduced into a jacket or a sleeve of the crystallization kettle for heating and evaporating saturated liquid, the generated secondary steam enters a steam jet pump, the temperature and the pressure of the secondary steam are raised again by the raw steam, and the secondary steam is sent to a steam heating plate on a circulating liquid circulating pipeline of a concentration tower for heat exchange, so that the utilization of the secondary steam is realized. The saturated solution in the evaporation crystallization kettle is continuously separated out along with the continuous reduction of the water content, and is discharged to centrifugal equipment after reaching the solid content of 30-40 percent.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A binary system evaporation crystallization method is characterized by mainly comprising the following steps:
waste liquid is pumped into a circulating liquid circulating pipeline (8) of the concentration tower, preheated, heated and heated, enters the concentration tower from the top of the concentration tower (4), circulating air enters the concentration tower from the bottom of the concentration tower (4) and is in countercurrent contact with the waste liquid, and moisture in the waste liquid is transferred to the air to realize concentration;
saturated high-temperature humid air formed at the top of the condensing tower (4) sequentially enters each condensing tower in the condensing tower group from the bottom of the condensing tower group (7) for condensation, and the formed condensed water is subjected to heat exchange and refrigeration and then is sprayed into the condensing tower as spray water of other condensing towers; introducing the air subjected to condensation treatment into the bottom of the concentration tower as the circulating air;
discharging the obtained unsaturated concentrated solution into a circulating solution circulating pipeline (8) of a concentration tower to be combined with the pumped waste liquid;
the obtained saturated concentrated solution is discharged into an evaporation crystallization kettle (14) at regular time for micro-negative pressure boiling evaporation, and the mixture obtained after evaporation is discharged into centrifugal equipment for solid-liquid separation to obtain salt crystals.
2. The dual system evaporative crystallization method of claim 1, wherein: the circulating liquid circulating pipeline (8) of the concentration tower comprises a high-temperature condensed water preheating heat exchanger (3) and a steam heater (10) which are sequentially communicated along the flowing direction of unsaturated concentrated liquid, the unsaturated concentrated liquid discharged from the bottom of the concentration tower enters the high-temperature condensed water preheating heat exchanger (3) as a cold side, one path of high-temperature condensed water formed by the condensation tower enters the high-temperature condensed water preheating heat exchanger (3) as a hot side, and preheating of the unsaturated concentrated liquid and refrigeration of the path of high-temperature condensed water are realized; the preheated unsaturated concentrated solution enters a steam heater (10) as a cold side, secondary steam obtained by the micro-negative pressure boiling evaporation of the evaporation crystallization kettle is injected by a steam jet pump to be pressurized and heated up and then enters the steam heater as a hot side, and the temperature of the circulating unsaturated concentrated solution can be raised to 80-85 ℃.
3. The dual system evaporative crystallization method of claim 1, wherein: the saturated concentrated solution in the evaporation crystallization kettle (14) is evaporated to 30-40% of solid content under the condition of micro-negative pressure boiling evaporation, and then discharged to external centrifugal equipment for solid-liquid separation to obtain salt crystals; the mother liquid is returned to the evaporation crystallization kettle for circulation and crystallization or is discharged out of the evaporation crystallization system.
4. The dual system evaporative crystallization method of claim 1, wherein: a liquid level sensor and a density sensor are positioned at the bottom in the concentration tower (4), and when the density of the liquid at the bottom of the concentration tower reaches a preset value, the concentration tower is controlled to discharge saturated concentrated liquid into the evaporation crystallization kettle; and when the density of the liquid at the bottom of the concentrated solution does not reach a preset value but reaches a preset minimum working liquid level, controlling the concentration tower to discharge unsaturated concentrated solution into the circulating liquid circulating pipeline of the concentration tower.
5. A dual system evaporative crystallization apparatus for use in the method of any one of claims 1 to 4, wherein: comprises a concentration tower (4), wherein an unsaturated concentrated solution discharge port (41) at the bottom of the concentration tower is communicated with the top of the concentration tower through a circulating liquid circulating pipeline (8) of the concentration tower; a saturated concentrated solution outlet (42) at the bottom of the concentration tower is communicated with a crystallization evaporation kettle (14) through a pipeline; a gas outlet (43) of the concentration tower at the top of the concentration tower is communicated with a condensed gas inlet at the bottom of a condensation tower group (7) through a pipeline;
the condensation tower group (7) comprises at least two condensation towers, and a condensate outlet at the bottom of each condensation tower is communicated with the tops of other condensation towers after passing through a pipeline and a heat exchange device; and a condensed gas outlet of a previous condensing tower in the condensing tower group (7) is communicated with a condensed gas inlet of a next condensing tower through a pipeline, and a condensed gas outlet of a condensing tower at the tail end is communicated with a gas inlet of a concentrating tower through a pipeline to form an air circulation loop.
6. The dual system evaporative crystallization apparatus of claim 5, wherein: the concentrating tower circulating liquid circulating pipeline (8) comprises a high-temperature condensed water preheating heat exchanger (3) and a steam heater (10) which are sequentially communicated along the flowing direction of unsaturated concentrated liquid, an unsaturated concentrated liquid discharge port (41) is communicated with a cold side inlet of the high-temperature condensed water preheating heat exchanger (3) through a pipeline and an evaporation tower circulating pump (2), a cold side outlet of the high-temperature condensed water preheating heat exchanger (3) is communicated with a cold side inlet of the steam heater (10) through a pipeline, and a cold side outlet of the steam heater is communicated with the top of the concentrating tower (4) through a pipeline.
7. The dual system evaporative crystallization apparatus of claim 6, wherein: and a cold side inlet of the high-temperature condensed water preheating heat exchanger (3) is communicated with a waste liquid source to be treated through a pipeline and a water inlet pump (1).
8. The dual system evaporative crystallization apparatus of claim 6, wherein: the condensation tower group (7) comprises a first condensation tower (71) and a second condensation tower (72), wherein a condensate discharge port at the bottom of the first condensation tower is communicated with a hot side pipeline inlet of the high-temperature condensate preheating heat exchanger (3) after passing through a pipeline and a high-temperature condensate circulating pump (11), and a hot side pipeline outlet is communicated with the top of the second condensation tower through a pipeline; and a condensate outlet at the bottom of the second condensing tower is communicated with a hot side pipeline inlet of a cooling plate type heat exchanger (13) after passing through a pipeline and a low-temperature condensate circulating pump (12), and an outlet of the hot side pipeline is communicated with the top of the first condensing tower.
9. The dual system evaporative crystallization apparatus of claim 8, wherein: a cold side inlet and a cold side outlet of the cooling plate type heat exchanger (13) are respectively communicated with an external cooling circulating water supply pipeline and a water return pipeline; and a water distributor (6) for spraying liquid is positioned at the top of each of the concentration tower (4), the first condensation tower (71) and the second condensation tower (72).
10. The dual system evaporative crystallization apparatus of claim 8, wherein: a secondary steam outlet of the crystallization evaporation kettle (14) is communicated with an injection interface of a steam injection pump (15) through a pipeline, and an outlet of the steam injection pump (15) is communicated with a hot side inlet of the steam heater (10); and the middle sections of the condensing towers in the condensing tower (4) and the condensing tower set (7) are provided with folded plate type structured packing (5) in a positioning way.
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