CN215049436U

CN215049436U - Triple-effect evaporation system for evaporating and extracting salt from coking wastewater

Info

Publication number: CN215049436U
Application number: CN202121092033.5U
Authority: CN
Inventors: 张合宾; 谷文彬; 范安林; 张建社
Original assignee: Jinneng Science and Technology Co Ltd
Current assignee: Jinneng Science and Technology Co Ltd
Priority date: 2021-05-20
Filing date: 2021-05-20
Publication date: 2021-12-07
Anticipated expiration: 2031-05-20

Abstract

The utility model provides a triple effect evaporation system that is used for coking wastewater evaporation to carry salt, wherein, the system includes: the system comprises a first-effect evaporation device, a second-effect evaporation device, a third-effect evaporation device, a first cyclone, a magma centrifugal separation device, a gas-liquid separator, a main cooler and an evaporation concentration condensing device; the evaporation concentration condensing device comprises a preheater and an evaporation condenser; the first-effect evaporation device comprises a first-effect separator, a first-effect heater and a first-effect circulating pump which form a circulating passage; the double-effect evaporation device comprises a double-effect separator, a double-effect heater and a double-effect circulating pump, wherein a circulating channel is formed in the double-effect separator; the triple-effect evaporation device comprises a triple-effect separator, a triple-effect heater and a triple-effect circulating pump which form a circulating passage. The utility model provides a this a triple effect evaporation system for salt is carried in coking wastewater evaporation can realize that the coking wastewater evaporation carries salt, and the coking wastewater evaporation carries the salt in-process both can prevent the calcium sulfate scale deposit, still can realize excellent energy-conserving purpose.

Description

Triple-effect evaporation system for evaporating and extracting salt from coking wastewater

Technical Field

The utility model relates to a triple effect evaporation system that is used for coking wastewater evaporation to carry salt belongs to evaporative concentration technical field.

Background

The coking wastewater is a type of wastewater with large production amount and extremely high treatment difficulty in the current coking production process; the composite material is complex in composition, contains toxic and highly toxic substances such as phenols and cyanides, aromatic hydrocarbons, polycyclic aromatic hydrocarbons, heterocyclic aromatic hydrocarbons and the like which are difficult to biodegrade, and also contains high-content suspended solids, chlorine, sulfate radicals, calcium and magnesium ions, and the main composition of the composite material is shown in the following table 1, so that the composite material is high-concentration organic industrial wastewater which is difficult to treat, and is one of the environmental protection problems in the coking industry.

The method for converting coking wastewater into solid salt by adopting an evaporation concentration method is an emerging treatment method in recent years, and the solid coking waste salt generated after treatment is mainly used for quenching coke and blending coal. The multi-effect evaporation is used as a traditional evaporation process, a plurality of evaporators are connected in series for operation based on the cascade utilization of steam, the heat energy utilization efficiency is high, the energy-saving effect is obvious, the system operation is safe and reliable, and the system has wide application value in the aspect of zero discharge of coking wastewater.

TABLE 1 coking high-salinity wastewater major ingredient table

1. Prior art relating to the present invention

1.1. Technical scheme of prior art I

Chinese patent CN111777118A discloses a triple-effect evaporation device for treating salt-containing wastewater, which comprises a feeding tank, a feeding pump, a primary-effect evaporation system, a secondary-effect evaporation system, a triple-effect evaporation system, a discharging pump, a steam condenser, a condensate water tank and a vacuum device; the first-effect evaporation system comprises a first-effect circulating pump, a first-effect separator and a first-effect heat exchanger, wherein the first-effect separator, the first-effect circulating pump and the first-effect heat exchanger form a circulating passage through a pipeline; the double-effect evaporation system comprises a double-effect circulating pump, a double-effect separator and a double-effect heat exchanger, wherein the double-effect separator, the double-effect circulating pump and the double-effect heat exchanger form a circulating passage through a pipeline; the triple-effect evaporation system comprises a triple-effect circulating pump, a triple-effect separator and a triple-effect heat exchanger, wherein the triple-effect separator, the triple-effect circulating pump and the triple-effect heat exchanger form a circulating passage through a pipeline;

the top of the feeding tank is provided with a feeding hole, the bottom of the feeding tank is provided with an outlet, the outlet is communicated with a bottom discharging pipe of the first-effect separator through a feeding pump and a pipeline, a discharging hole of the first-effect circulating pump is communicated with a bottom discharging pipe of the second-effect separator through a pipeline, a discharging hole of the second-effect circulating pump is communicated with a bottom discharging pipe of the third-effect separator through a pipeline, and a discharging hole of the third-effect circulating pump is communicated with a discharging pump through a pipeline; a hydrometer is arranged on the feeding tank, and a measuring head of the hydrometer extends into the feeding tank;

the shell pass inlet of the primary heat exchanger is communicated with a steam pipeline, and the shell pass outlet of the primary heat exchanger is communicated with a steam condenser through a pipeline; an outlet at the top of the primary-effect separator is communicated with a shell pass inlet of the secondary-effect heat exchanger, and a shell pass outlet of the secondary-effect heat exchanger is communicated with the steam condenser through a pipeline; the top outlet of the two-effect separator is communicated with the shell pass inlet of the three-effect heat exchanger, and the shell pass outlet of the three-effect heat exchanger is communicated with the steam condenser through a pipeline; the outlet of the steam condenser is communicated with a condensed water tank, and the top outlet and the bottom outlet of the condensed water tank are respectively connected with a vacuum pump and a condensed water pump through pipelines.

The device has a simple structure, and when the device is used for treating salt-containing wastewater, pretreatment steps such as softening and the like can be omitted, on one hand, the supersaturation degree of salts such as calcium sulfate and the like can be eliminated in time by regularly adding calcium sulfate crystal seeds into the feeding tank, and on the other hand, the sufficient circulating flow rate and material circulating amount in the three evaporation units are ensured by the forced circulating pump, so that the purpose of preventing scaling is achieved; meanwhile, the first-effect evaporation system adopts steam as a heat source, and the second-effect evaporation system and the third-effect evaporation system respectively adopt secondary steam of the first-effect evaporation system and secondary steam of the second-effect evaporation system as heat sources, so that heat energy is fully utilized, and the steam energy consumption is low.

1.2. Disadvantages of the first prior art

(1) The heat recovery mode is not set up reasonably. On one hand, the heat carried by the hot distilled water generated by each heat exchanger is not recovered; on the other hand, the secondary steam extracted from the top of the triple-effect separator is subjected to heat exchange, cooling and cooling in the steam condenser by using circulating water, about 20-25% of heat of the whole device is evaporated and wasted by the circulating water, and a large amount of heat carried by the triple-effect secondary steam is not recycled, so that not only is the steam consumption of the whole device high, but also the water supplement amount of the circulating water is increased, and the waste of resources is caused;

(2) the device configuration is incomplete, and the technological requirements of evaporation, concentration crystallization and solid-liquid separation on the coking wastewater cannot be realized. In addition, the content of suspended solid and organic matters in the coking wastewater is high, the device lacks pretreatment means such as flocculation and filtration on raw water, the content of suspended solid and organic matters in materials of the three-effect separator is easily too high, and the three-effect circulating liquid is subjected to bumping so as to cause unqualified produced distilled water; too high suspended solid in the triple-effect circulating liquid can also cause the triple-effect crystallization to be too fine, thereby causing poor centrifugal effect and further causing the solid-liquid separation to be impossible in serious cases;

(3) the calcium sulfate crystal seeds are added into the feeding tank periodically, so that the material consumption cost of concentrated water evaporation is increased, and the discharge amount of solid wastes is increased.

2. Prior art relating to the present invention

2.1. Technical scheme of prior art II

Chinese patent CN107151035A discloses a salt extraction system and a salt extraction method for coal chemical industry desulfurization wastewater, wherein the salt extraction system for coal chemical industry desulfurization wastewater comprises a multi-effect separator, a multi-effect heater, a condenser and a vacuum pump, the multi-effect separator comprises a forced circulation evaporation device with three effects connected in sequence, a feed inlet of the forced circulation evaporation device with one effect is communicated with a preheater, and a discharge end of the forced circulation evaporation device with three effects is communicated with a cooling crystallizer; the multi-effect heater comprises heaters which are sequentially connected by three effects, the first-effect heater is also communicated with the feed end of the first-effect forced circulation evaporation device, the air inlet of the second-effect heater is communicated with the air outlet at the top of the first-effect forced circulation evaporation device, the air outlet of the second-effect heater is communicated with the feed end of the second-effect forced circulation evaporation device, the air inlet of the third-effect heater is communicated with the air outlet at the top of the second-effect forced circulation evaporation device, and the air outlet of the third-effect heater is communicated with the feed end of the third-effect forced circulation evaporation device; the condenser is communicated with an exhaust port at the top of the triple-effect forced circulation evaporation device through a pipeline, and the vacuum pump is arranged on an air exhaust pipeline of the condenser; the system also comprises a gas-liquid separator arranged between the first-effect forced circulation evaporation device and the second-effect heater, wherein a gas inlet of the gas-liquid separator is connected with a gas outlet at the top of the first-effect forced circulation evaporation device, and a gas outlet of the gas-liquid separator is connected with a gas inlet of the second-effect heater; the system also comprises a plurality of axial-flow pumps which are correspondingly arranged with the forced circulation evaporation devices sequentially connected with the triple effect, and the plurality of axial-flow pumps are respectively arranged between the forced circulation evaporation devices and the heaters.

2.2. The second prior art has the defects

(1) The heat recovery of the device is not thorough enough, and the overall energy consumption is higher. Specifically, although the device recycles the heat of the high-temperature condensed water separated by the vapor-liquid separator for heating raw water, all the steam extracted from the top of the triple-effect forced circulation evaporation device is not condensed and recycled in the condenser, and a large amount of heat carried by the steam is not recycled (the medium used for cooling the steam is not described), about 15-20% of the heat of the whole device is wasted, so that not only is the steam consumption of the whole device high, but also energy is wasted;

(2) the device lacks necessary calcium sulfate scale deposit device, and it is big to handle the coking wastewater degree of difficulty that contains higher concentration calcium ion, sulfate radical, has the risk that can't obtain solid crystal salt. On one hand, the device has high operation temperature, the one-effect operation temperature reaches 100-;

(3) the device is only suitable for treating salt-containing wastewater with high ammonium sulfate salt content, low solid suspended matter content and low COD content, and can not meet the process requirements of evaporation, concentration crystallization and solid-liquid separation on coking wastewater. Specifically, the content of suspended solid and organic matters in the coking wastewater is high, the device lacks pretreatment means such as flocculation and filtration on raw water, the content of suspended solid and organic matters in materials of the three-effect separator is easily too high, and the produced distilled water is unqualified due to the fact that the three-effect circulating liquid is subjected to bumping; in addition, too high suspended solid in the triple-effect circulating liquid can also lead to too fine triple-effect crystallization, further lead to poor centrifugal effect and further lead to the incapability of realizing solid-liquid separation in severe cases.

Therefore, providing a novel triple-effect evaporation system and process for evaporating and extracting salt from coking wastewater has become a technical problem to be solved urgently in the field.

SUMMERY OF THE UTILITY MODEL

In order to solve the defects, the utility model aims to provide a triple-effect evaporation system for evaporating and extracting salt from coking wastewater. The utility model provides a this a triple effect evaporation system for salt is carried in coking wastewater evaporation can realize that the coking wastewater evaporation carries salt, and the coking wastewater evaporation carries the salt in-process both can prevent the calcium sulfate scale deposit, still can realize excellent energy-conserving purpose.

In order to achieve the above object, the utility model provides a triple effect evaporation system for salt is carried in coking wastewater evaporation, wherein, triple effect evaporation system for salt is carried in coking wastewater evaporation includes:

the system comprises a first-effect evaporation device, a second-effect evaporation device and a third-effect evaporation device, wherein the first-effect evaporation device comprises a first-effect separator, a first-effect heater and a first-effect circulating pump which form a circulating passage; the double-effect evaporation device comprises a double-effect separator, a double-effect heater and a double-effect circulating pump which form a circulating passage; the triple-effect evaporation device comprises a triple-effect separator, a triple-effect heater and a triple-effect circulating pump which form a circulating passage;

wherein the system further comprises: the system comprises a first cyclone, a crystal slurry centrifugal separation device, a gas-liquid separator, a main cooler and an evaporation concentration condensing device; the evaporation concentration condensing device comprises a preheater and an evaporation condenser;

a cold side inlet of the preheater is communicated with a coking wastewater pipeline, a cold side outlet of the preheater is communicated with a spraying device inlet at the top of the evaporative condenser, and a circulating water tank at the bottom of the evaporative condenser forms a circulating passage with the evaporative cold circulating pump and the spraying device of the evaporative condenser through pipelines; the outlet of the circulating water tank at the bottom of the evaporative condenser is also communicated with the feed inlet of the primary effect separator through a pipeline;

the shell pass inlet of the first-effect heater is communicated with a steam pipeline, and the shell pass outlet of the first-effect heater is communicated with the condensed water inlet of the second-effect heater through a pipeline; a steam outlet of the first-effect separator is communicated with a steam inlet of the second-effect heater, and a shell pass outlet of the second-effect heater is communicated with a condensed water inlet of the third-effect heater through a pipeline; a steam outlet of the two-effect separator is communicated with a steam inlet of the three-effect heater, a shell pass outlet of the three-effect heater is communicated with the main cooler through a pipeline, a steam outlet of the three-effect separator is communicated with an inlet of a heat exchange pipe of the evaporative condenser through the gas-liquid separator through a pipeline, and an outlet of the heat exchange pipe is communicated with an inlet of the main cooler;

a feed inlet of the first-effect circulating pump is communicated with an inlet of a first cyclone through a first-effect concentrated liquid pump by a pipeline, and a light component outlet and a heavy component outlet of the first cyclone are respectively communicated with a feed inlet of the second-effect separator and a feed inlet of the first-effect circulating pump by pipelines; a feed inlet of the two-effect circulating pump is communicated with a feed inlet of the three-effect separator through a two-effect concentrated liquid pump through a pipeline; the feed inlet of the triple-effect circulating pump is communicated with the crystal slurry centrifugal separation device through a crystal slurry extraction pump through a pipeline.

The utility model discloses in, add vapour and liquid separator between triple effect separator and evaporative condenser, can carry out gas-liquid separation to triple effect steam earlier before getting into evaporative condenser to avoid triple effect separator inside the appearance to explode and boil and then lead to the distilled water to go out the water conductivity and exceed standard.

The utility model discloses in, evaporative condenser (for short evaporate cold) is conventional equipment, the cold upper portion of evaporation is equipped with fan, sprinkler and heat exchange tube, and the bottom is equipped with circulating water tank.

The utility model discloses in, the feed inlet of a separator, two effect separators and three effect separators all is located the lower part of each effect separator, and further ground, the feed inlet all is located below the liquid level of each effect separator.

The utility model discloses in, the flow of each effect circulating pump used is great, can reach 2000m³More than h, and meanwhile, the circulation requirement of each effect can be met only by a lift of about 3-4m in the running process of each effect circulating pump, so that the outlet pressure of each effect circulating pump is only 0.03-0.04MPa, and the flow dividing effect of the cyclone is poor under the pressure. Therefore, in the system in add one and imitate concentrate pump, two effect concentrate pump, magma extraction pump, one imitate concentrate pump, two effect concentrate pump, magma extraction pump and all be used for the forwarding of material, set up its aim at: on the premise of ensuring the conveying pressure of the materials containing crystals and the flow dividing effect of the cyclone, the lifts of the first-effect circulating pump, the second-effect circulating pump and the third-effect circulating pump are reduced to the maximum extent, and the purpose of reducing power consumption is achieved.

The utility model discloses in, main cooler bottom is equipped with the conductivity detector, and the probe of conductivity detector deepens below the liquid level in the main cooler.

As a specific embodiment of the above system of the present invention, wherein the centrifugal separation device for crystal slurry comprises a second cyclone, a cooling crystallizer and a centrifuge; a feed inlet of the triple-effect circulating pump is communicated with an inlet of the second cyclone through a crystal slurry extraction pump by a pipeline, and a light component outlet and a heavy component outlet of the second cyclone are respectively communicated with the feed inlet of the triple-effect circulating pump and an inlet of the cooling crystallizer by pipelines; the outlet of the cooling crystallizer is communicated with the inlet of the centrifuge through a pipeline.

The utility model discloses in, the cooling crystallizer is jacket structure, and the adoption temperature is the concentrated water cooling about 32 ℃ in the clamp cover, and the concentrated water after the intensification is sent to an effect separator and is carried the raw materials of salt as the evaporation.

The utility model discloses in, the top of cooling crystallizer is equipped with the agitator for prevent that the crystallization material from subsiding and blockking up pipeline and equipment.

The utility model discloses in, the preferred horizontal spiral sedimentation centrifuge of centrifuge.

As a specific embodiment of the above system, wherein, the export of the bottom circulating water tank of the evaporative condenser is communicated with the water inlet of the water side inlet of the main cooler and the water inlet of the cooling crystallizer respectively through the concentrated water pump through the pipeline, and the water outlet of the water side outlet of the main cooler and the water outlet of the cooling crystallizer are communicated with the feed inlet of the one-effect separator through the pipeline after being collected. Correspondingly, raw water is circularly sprayed in the evaporative condenser, concentrated water with the mass concentration of 8.5-9.5% and the temperature of 20-35 ℃ is obtained in a circulating water tank at the bottom of the evaporative condenser, the concentrated water is pressurized by a concentrated water pump and then is respectively sent to a main cooler and a cooling crystallizer, on one hand, the temperature of the two devices is reduced, on the other hand, the concentrated water is heated to recover partial heat, and the heated concentrated water is sent to a feed inlet of a first-effect separator to be used as a raw material for evaporation and salt extraction treatment.

As the utility model discloses above a concrete implementation of system, wherein, the export of dense water pump is equipped with the teletransmission thermometer for detect the temperature of supplying dense water outward.

As a specific embodiment of above the system of the utility model, wherein, the bottom of main cooler is equipped with the distilled water jar, and the export of distilled water jar passes through the pipeline and imports the intercommunication via the hot side of distilled water pump with the preheater, and the hot side export of preheater sends the pipeline intercommunication outward with the distilled water.

As a specific embodiment of the above system of the present invention, wherein the top outlet of the main cooler is communicated with the vacuum pump through a pipeline to ensure that the vacuum gauge pressure of the system is-85 kPa to-95 kPa.

As a specific embodiment of the above system of the present invention, wherein the steam pipeline is sequentially provided with a steam regulating valve and a steam ejector. The utility model discloses an in the embodiment, outside steam gets into the high pressure import of steam ejector after the steam control valve pressure regulating, and steam ejector's export is passed through steam conduit and is imitated heater shell side import intercommunication to send steam to the shell side of an effect heater.

As a specific embodiment of the above system, wherein, the steam outlet of the two-effect separator is equipped with the bypass interface, the bypass interface pass through the pipeline with the low pressure steam inlet intercommunication of steam ejector.

As a specific embodiment of the above system of the present invention, wherein the first effective heater comprises two parallel heaters. When the effect of one heater is reduced, the heater can be independently stopped, and the heater can be cleaned without stopping production.

As a specific embodiment of the above system of the present invention, the system further comprises a pretreatment device, wherein the pretreatment device comprises a settling tank, a raw water tank and a plate-and-frame filter press; wherein, the top of the settling tank is provided with a feed inlet, the middle part is provided with an outlet, and the bottom is provided with a sludge discharge port; an outlet of the settling tank is communicated with an inlet at the top of the raw water tank through a pipeline, and an outlet at the bottom of the raw water tank is communicated with a cold side inlet of the preheater through a raw water pump through a pipeline; the sludge discharge port is communicated with the inlet of the plate-and-frame filter press through a filter pump by a pipeline, and the filtered water outlet of the plate-and-frame filter press is communicated with the inlet at the top of the raw water tank by a pipeline.

As a specific embodiment of the above system, wherein, the side of the raw water tank is provided with a pH meter, and the probe of the pH meter is deep below the liquid level in the raw water tank for detecting the pH value of the raw water.

As the present invention provides a specific embodiment of the above system, wherein, the crystal slurry centrifugal separation device further comprises a mother liquid tank, a mother liquid pump, the mother liquid outlet of the centrifuge is communicated with the mother liquid tank inlet through a pipeline, and the outlet of the mother liquid tank is communicated with the inlet of the settling tank through the mother liquid pump.

As a specific embodiment of the above system, wherein the cooling water outlet of the gas-liquid separator is communicated with the top inlet of the raw water tank through a pipeline, so as to deliver the cooling water separated by the gas-liquid separator to the raw water tank.

As a specific embodiment of the above system of the present invention, in which the distilled water pipeline of the first-effect heater, the distilled water pipeline of the second-effect heater and the distilled water pipeline of the third-effect heater (i.e. the pipeline connected to the shell side outlet of each-effect heater) are respectively provided with a U-shaped water seal, so as to ensure that the steam pressure in the shell side of each-effect heater is in a stable state;

preferably, the water seal height of the U-shaped water seal is not less than 1.5 m.

The utility model provides an among the system, one imitates evaporation plant, two imitate evaporation plant, three imitate evaporation plant, vapour and liquid separator, steam jet ware, swirler etc. and are conventional equipment.

The system can be applicable to the triple effect evaporation technology of multiple difference and carry out the evaporation of coking wastewater and carry salt, it is right in order to further the utility model discloses a system explains, the utility model discloses still provides and uses the utility model discloses a system carries out the triple effect evaporation technology that evaporates and carry salt to coking wastewater, wherein, the technology includes following step:

(1) after heat exchange and temperature rise are carried out on the pretreated coking wastewater in a preheater, the pretreated coking wastewater is sent to an evaporative condenser and is subjected to heat exchange with triple-effect secondary steam in the evaporative condenser, the pretreated coking wastewater is heated, continuously evaporated and concentrated in the heat exchange process to obtain concentrated water, and the concentrated water is sent to a single-effect separator to be used as a raw material for evaporation and salt extraction;

(2) concentrated water is continuously pumped by a first-effect circulating pump, exchanges heat with external steam in a first-effect heater and then enters a first-effect separator for evaporation to generate first-effect secondary steam and first-effect concentrated solution;

(3) the first-effect concentrated solution is extracted by a first-effect concentrated solution pump and then is sent to a first cyclone for classification treatment, after treatment, the upper layer is low-solid-content solution, and the lower layer is high-solid-content calcium sulfate slurry; feeding the calcium sulfate slurry back to a feeding hole of the one-effect circulating pump to continuously participate in circulation; the low solid content solution enters a feed inlet of the two-effect separator and is continuously pumped in the two-effect heater by the two-effect circulating pump to exchange heat with condensed water and a small amount of non-condensable gas generated after heat exchange of the primary secondary steam and external steam in the two-effect heater, and then the condensed water and the small amount of non-condensable gas enter the two-effect separator to be evaporated to generate secondary steam and secondary concentrated solution;

(4) the secondary-effect concentrated solution is extracted by a secondary-effect concentrated solution pump and then is sent to a feed inlet of a tertiary-effect separator, and is continuously pumped in a tertiary-effect heater by a tertiary-effect circulating pump to exchange heat with part of secondary steam and condensed water and a small amount of non-condensable gas generated after heat exchange in the secondary-effect heater, and then the condensed water and the small amount of non-condensable gas enter the tertiary-effect separator to be evaporated again, so that tertiary-effect secondary steam and tertiary-effect crystal slurry are generated; condensed water and a small amount of non-condensable gas generated after heat exchange enter a main cooler for heat exchange and temperature reduction so as to recover distilled water and heat;

(5) and the crystal slurry is extracted by a crystal slurry extraction pump and then enters a crystal slurry centrifugal separation device, and solid salt and mother liquor are obtained after grading, cooling crystallization and centrifugal separation treatment in the crystal slurry centrifugal separation device.

As a specific implementation mode of the above process of the present invention, wherein the total dissolved solids mass concentration (TDS content) in the coking wastewater is about 6% -8%, and the suspended solids concentration is 300mg/L in 100-.

As the utility model discloses above a concrete implementation of technology, wherein, technology still includes carries out the preliminary treatment to coking wastewater, the preliminary treatment includes: settling and filtering the coking wastewater by using the pretreatment device to obtain pretreated coking wastewater (marked as raw water) and filter residues, and carrying out coal blending treatment on the filter residues after squeezing and dewatering.

As a specific implementation mode of the above process of the present invention, the concentration of suspended matters in the pretreated coking wastewater is less than 30mg/L based on the total volume of the pretreated coking wastewater. The utility model discloses in, make suspended solid concentration <30mg/L in the former aquatic can reduce the COD content of triple effect magma, prevent that triple effect separator from bumping, prevent that the crystallized salt particle diameter undersize.

As the utility model discloses above a concrete implementation mode of technology, wherein, in step (1), send the raw water after the heat transfer intensifies to evaporative condenser and make it carry out the heat transfer with triple effect steam in evaporative condenser, among the heat transfer process, coking wastewater after the preliminary treatment is heated and constantly evaporates, is concentrated, obtains dense water, include:

conveying the raw water subjected to heat exchange and temperature rise to the top of an evaporative condenser for spraying, continuously extracting and spraying the raw water by an evaporative cold circulating pump, exchanging heat with triple-effect secondary steam in a heat exchange pipe of the evaporative condenser, heating the raw water in the heat exchange process, continuously evaporating and concentrating the raw water, and continuously extracting to obtain concentrated water;

and cooling the triple-effect secondary steam in the heat exchange pipe of the evaporative condenser into distilled water and a small amount of non-condensable gas, and sending the distilled water and the small amount of non-condensable gas to the main cooler for further cooling.

As a specific embodiment of the above process of the present invention, wherein, in step (1), the temperature of the pretreated coking wastewater (i.e. raw water) is 30-50 ℃, the temperature is too low to increase the energy consumption of the system, and the temperature is too high to reduce the pretreatment effect and increase the volatilization of the odor.

As a specific embodiment of the above process of the present invention, wherein, in step (1), the triple-effect secondary steam is obtained by performing gas-liquid separation by using a gas-liquid separator, and the cooling water obtained by the separation can be sent to the raw water tank of the pretreatment device for re-evaporation. And the triple-effect secondary steam is subjected to gas-liquid separation and then sent to the evaporative condenser, so that the phenomenon that the conductivity of the outlet water of the distilled water exceeds the standard due to the explosive boiling in the triple-effect separator can be avoided.

In the step (1), raw water subjected to heat exchange and temperature rise exchanges heat with triple-effect secondary steam subjected to gas-liquid separation in an evaporative condenser, and in the heat exchange process, pretreated coking wastewater is heated, continuously evaporated and concentrated to obtain concentrated water; the triple-effect secondary steam exchanges heat with raw water to obtain condensed water and a small amount of non-condensable gas, the condensed water and the small amount of non-condensable gas are sent into a main cooler to be subjected to heat exchange and temperature reduction with low-temperature concentrated water produced in an evaporative condenser, the temperature of the cooled non-condensable gas is less than or equal to 35 ℃, the cooled non-condensable gas is pumped out by a vacuum pump so as to always keep the vacuum degree in the triple-effect separator at-85 kPa to-95 kPa, such as about-90 kPa; and the recovered condensed water (distilled water) is collected in a distilled water tank at the bottom of the main cooler, the condensed water is pressurized by a distilled water pump and then enters a preheater for heat exchange, and the generated distilled water is finally reused for replenishing water of a production system.

As a specific embodiment of the above process of the present invention, wherein the mass concentration of the total dissolved solids in the concentrated water is 8.5% to 9.5%, and the temperature is 20 ℃ to 35 ℃.

As the utility model discloses above a concrete implementation of technology, wherein, heat transfer to the coking wastewater after the preliminary treatment heaies up in the pre-heater, include:

and starting a raw water pump to ensure that the raw water exchanges heat with the distilled water in the preheater and the temperature is raised. The distilled water can be distilled water in a distilled water tank arranged at the bottom of the main cooler, and is sent to a hot side inlet of the heat exchanger through a distilled water pump.

As a specific embodiment of the above process of the present invention, wherein the process further comprises after step (1): the concentrated water is pressurized by a concentrated water pump and then exchanges heat and heats in a main cooler and a cooling crystallizer respectively, and the heated concentrated water is sent to a one-effect separator as a raw material.

As a specific implementation manner of the above process of the present invention, in the step (2), the concentrated water is continuously pumped by the first-effect circulating pump and enters the first-effect separator for evaporation after exchanging heat with the mixed gas of the external steam and part of the second-effect secondary steam in the first-effect heater;

preferably, the pressure of the mixed gas is 60-70kPa, and the temperature is 86-90 ℃.

As the utility model discloses above a concrete implementation mode of technology, wherein, in step (2), the outside steam (low pressure waste heat steam) that comes from the outer net gets into the high pressure import of steam ejector after steam control valve carries out the decompression and adjusts, and the two effect steam of part gets into through the pipeline the low pressure steam import of steam ejector mixes in steam ejector inside and outside steam and the two effect steam of part, and the gained mist gets into one and imitates the heater and carry out the heat transfer.

The utility model discloses obtain the mist with the mixing of outside steam and part two-effect steam, and will the mist is sent into one and is imitated the heater and carry out the heat transfer, can retrieve the heat of part two-effect steam.

As a specific embodiment of the above process of the present invention, wherein the mass concentration of the total dissolved solids in the first-effect concentrated solution is 12% to 13%.

As a specific embodiment of the above process of the present invention, the temperature of the first-effect concentrated solution is less than or equal to 78 ℃, preferably 76-78 ℃. The utility model discloses in will the temperature control of a effect concentrate can prevent that the high temperature from causing calcium sulfate to separate out in a large number for being less than or equal to 78 ℃, blocks up equipment.

Sulfate radicals and calcium ions in the coking wastewater can be separated out in a calcium sulfate solid form in a one-effect evaporation device, the one-effect concentrated solution is treated by a first cyclone, calcium sulfate slurry is sent back to a feed inlet of a one-effect circulating pump to continuously participate in circulation, the concentration of calcium sulfate solids in one-effect circulating solution (namely circulating solution related to a one-effect separator) can be increased, the sufficient number of crystal seeds can be ensured in one-effect material flow, calcium sulfate in the salt solution is not deposited on the wall surface of a pipeline in the evaporation process, but preferentially attached to the surface of suspended calcium sulfate crystal seeds, and the purpose of preventing scaling is achieved.

As a specific implementation manner of the above process of the present invention, wherein the temperature of the condensed water and a small amount of non-condensable gas generated by the external steam in the first-effect heater after heat exchange is higher than the temperature of the first-effect secondary steam by about 3 to 6 ℃, so that the condensed water and a small amount of non-condensable gas generated by the external steam after heat exchange in step (3) can enter the shell pass of the second-effect heater to exchange heat with the low solid content solution in the tube pass together with the first-effect secondary steam, so as to fully recover the heat of the condensed water and the non-condensable gas;

when the U-shaped water seal is arranged on the distilled water pipeline of the primary effect heater, condensed water generated by heat exchange of external steam and a small amount of non-condensable gas enter the shell pass of the secondary effect heater to perform heat exchange and temperature reduction after passing through the U-shaped water seal, and the arrangement of the U-shaped water seal can ensure that the steam pressure in the shell pass of the primary effect heater is in a stable state.

As a specific embodiment of the above process of the present invention, in the step (3), the temperature of the secondary steam is 64-68 ℃.

As a specific implementation manner of the above process of the present invention, in the step (3), the mass concentration of the total dissolved solids in the two-effect concentrated solution is 22% to 22.5%.

Wherein, the utility model discloses do not do the specification to the solid content of low solid content solution and high solid content calcium sulfate thick liquid in step (3), technical personnel in the field can be judged conventionally that one imitates the concentrate and send to first swirler after the concentrated liquid pump is adopted to carry out the stage treatment after the upper strata is low solid content solution, and the lower floor is high solid content calcium sulfate thick liquid.

As a specific implementation manner of the above process of the present invention, in step (4), the mass concentration of the total dissolved solids in the crystal slurry is 45% to 55%.

As a specific embodiment of the above process of the present invention, wherein, in the step (4), the temperature of the triple-effect secondary steam is 48-52 ℃.

The utility model discloses above in step (4) of technology, the condensate water that generates after the heat transfer and a small amount of noncondensable gas get into main cooler and carry out the heat transfer cooling to retrieve distilled water and heat. When the distilled water pipeline of the triple-effect heater is provided with the U-shaped water seal, condensed water and a small amount of non-condensable gas generated after heat exchange enter the main cooler to carry out heat exchange and temperature reduction after the U-shaped water seal, and the arrangement of the U-shaped water seal can ensure that the steam pressure in the shell pass of the triple-effect heater is in a stable state; in addition, the cooling medium used for heat exchange and temperature reduction can be low-temperature concentrated water produced in an evaporative condenser, the temperature of the cooled non-condensable gas is less than or equal to 35 ℃, the cooled non-condensable gas can be pumped out by a vacuum pump, so that the vacuum degree in the three-effect separator is always kept between-85 kPa and-95 kPa, such as about-90 kPa; and the recovered condensed water (distilled water) is collected in a distilled water tank at the bottom of the main cooler, the condensed water is pressurized by a distilled water pump and then enters a preheater for heat exchange, and the generated distilled water is finally reused for replenishing water of a production system.

As a specific embodiment of the above-mentioned technology of the present invention, wherein, the circulating flow rate of the circulating fluid in the tube pass of the first-effect heater, the second-effect heater and the third-effect heater is not less than 2m/s through each effective circulating pump respectively, so as to achieve the purpose of preventing scaling.

As the utility model discloses above a concrete implementation mode of technology, wherein, step (5) the magma gets into magma centrifugal separation device after being adopted by magma extraction pump, and in obtain solid salt and mother liquor after grading, cooling crystallization and centrifugal separation processing in the magma centrifugal separation device, include:

and the crystal mush is extracted by a crystal mush extraction pump and then is sent to a second swirler for classification treatment, the upper layer is a low solid content solution after the treatment, the lower layer is a high solid content solution, the low solid content solution returns to a feed inlet of the three-effect circulating pump for continuous circulation, the high solid content solution enters a cooling crystallizer for cooling crystallization, and then is centrifugally separated in a centrifuge to obtain solid salt and mother liquor.

Wherein, the utility model discloses do not do the specification requirement to the solid content of low solid content solution and high solid content solution, technical personnel in the field can routinely judge that the magma carries out stage treatment back upper strata at the second swirler and be low solid content solution, and the lower floor is high solid content solution.

The utility model discloses above the technology in, will low solid content solution returns triple effect separator outlet pipeline and continues to circulate and on the one hand can improve the output of solid material especially suspended solid such as calcium sulfate, mud in the triple effect circulation liquid, reduces the probability that triple effect separator explodes and boils, and on the other hand can improve the solid content in the cooling crystallizer, reduces the mother liquor discharge that produces after the centrifugation.

As a specific implementation manner of the above process of the present invention, the temperature of the condensed water and a small amount of non-condensable gas generated after heat exchange in the dual-effect heater is higher by about 3-6 ℃ than the temperature of the dual-effect secondary steam, so in step (4), the condensed water and a small amount of non-condensable gas generated after heat exchange in the dual-effect heater can enter the shell pass of the triple-effect heater to exchange heat with the dual-effect concentrated solution in the tube pass together with part of the dual-effect secondary steam, so as to fully recover the heat of the condensed water and the non-condensable gas;

when the U-shaped water seal is arranged on the distilled water pipeline of the double-effect heater, condensed water and a small amount of non-condensable gas generated after heat exchange in the double-effect heater enter the shell pass of the triple-effect heater through the U-shaped water seal to carry out heat exchange and temperature reduction, and the arrangement of the U-shaped water seal can ensure that the steam pressure in the shell pass of the double-effect heater is in a stable state.

As a specific embodiment of the above process of the present invention, wherein the temperature of the obtained outlet crystal slurry is 35-45 ℃ after cooling and crystallizing in step (5).

As a specific embodiment of the above process of the present invention, wherein, after the cooling and crystallization in step (5), the solid content of the obtained outlet crystal slurry is 30% to 50%, so that the dissolved salt in the crystal slurry (salt slurry) is rapidly separated out, and the salt yield is increased.

As a specific embodiment of the above process of the present invention, wherein the cooling medium used for cooling crystallization in step (5) is low-temperature concentrated water produced in an evaporative condenser, and the temperature of the cooling medium is 20-32 ℃.

In a specific embodiment of the present invention, step (5) includes the following specific steps:

the crystal mush is extracted by a crystal mush extraction pump and then is sent to a second swirler for classification treatment, the upper layer after treatment is a low solid content solution, the lower layer is a high solid content solution, the low solid content solution returns to a three-way separator for continuous circulation, the high solid content solution enters a cooling crystallizer, the high solid content solution exchanges heat with low-temperature concentrated water in a cooling crystallizer interlayer under the stirring condition, after cooling crystallization, the temperature of the obtained outlet crystal mush is 35-45 ℃, the solid content is 30% -50%, and then the outlet crystal mush is sent to a centrifuge for centrifugal separation to obtain solid salt and mother liquor;

returning part of the mother liquor to the pretreatment process of the coking wastewater, and mixing the part of the mother liquor with the coking wastewater and then carrying out sedimentation and centrifugation again to increase the yield of solid salt; and part of mother liquor can be periodically extracted for coal blending treatment so as to prevent the triple-effect separator from bumping due to overhigh COD.

The utility model provides a triple effect evaporation system and technology for salt is carried in coking wastewater evaporation can reach following unexpected technological effect:

(1) the utility model discloses a unique energy-conserving design, made the steam unit consumption of system reduce by a wide margin. Specifically, on one hand, a set of steam ejector is additionally arranged in the system, 0.6MPa of external steam is used as power, and part of secondary steam in the secondary effect returns to the primary effect heater again for heating, so that the pressure of the secondary steam in the secondary effect is greatly improved, the enthalpy value of the secondary steam in the secondary effect is greatly utilized, and the use amount of the external steam is reduced; on the other hand, the pretreated raw water is used for replacing circulating water or low-temperature water as circulating cooling water for evaporating cold to cool the triple-effect secondary steam, wherein the heat of the triple-effect secondary steam is used for heating and concentrating the raw water, the circularly evaporated raw water is used for cooling the triple-effect secondary steam, one part of heat is used for two times, the heat utilization efficiency is greatly improved, distilled water is recovered, and a large amount of heat is recovered. In conclusion, the utility model fully utilizes the heat energy of the steam, the steam consumption of the evaporation waste water is only about 260 kg/ton water, and the steam consumption (320-340 kg/ton water) is reduced by more than 18 percent compared with the steam consumption of the conventional three-effect evaporation system;

(2) the system provided by the utility model fully considers the characteristics of the coking wastewater, and omits the conventional softening pretreatment step; the first cyclone is utilized to recover the calcium sulfate crystal seeds, so that the supersaturation of salts such as calcium sulfate and the like can be eliminated in time, and meanwhile, the anti-scaling purpose is realized by combining the modes of controlling the heating temperature (namely the temperature of the first-effect concentrated solution is less than or equal to 78 ℃), reasonably designing the circulating flow and the like; in addition, a first-effect heater easy to scale is changed into two heaters which are connected in parallel to operate, so that online cleaning without stopping production is realized, the whole system operates stably, and the cleaning period is greatly prolonged;

(3) the utility model discloses the partial mother liquor after will centrifuging is used for the system again to evaporate and produce salt to adopt preprocessing device to subside and filter coking high salt waste water, improved solid salt output, reduced the mother liquor emission, avoided because of the too high bumping and the too thin problem of crystallization that causes of triple effect magma COD, can also guarantee centrifuge's continuous effective operation simultaneously.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a triple-effect evaporation system for evaporating and extracting salt from coking wastewater provided by the embodiment of the utility model.

The main reference numbers illustrate:

in fig. 1:

1. an evaporative condenser; 2. a first effect separator; 3. a two-effect separator; 4. a three-effect separator; 5. a primary heater; 6. a dual-effect heater; 7. a triple effect heater; 8. a one-effect circulation pump; 9. a two-effect circulating pump; 10. a three-effect circulating pump; 11. a first effect concentrate pump; 12. a two-way concentrate pump; 13. a crystal slurry extraction pump; 14. a steam regulating valve; 15. a steam jet device; 16. a main cooler; 17. a vacuum pump; 18. a distilled water pump; 19. cooling the crystallizer; 20. a centrifuge; 21. a first swirler; 22. a second swirler; 23. an evaporative cooling circulation pump; 24. a preheater; 25. a gas-liquid separator; 26. a concentrate pump.

Detailed Description

The following detailed description of the embodiments and the advantageous effects thereof will be provided by way of specific examples and accompanying drawings, which are provided to assist the reader in better understanding the nature and features of the present invention, and are not intended to limit the scope of the present invention.

It should be noted that the term "comprises/comprising" and any variations thereof in the description and claims of the present invention and the above-described drawings is intended to cover non-exclusive inclusions, such that a process, method, process, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, process, system, article, or apparatus.

In the present invention, the terms "upper", "lower", "inner", "middle", "top" and "bottom" indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings. These terms are used primarily to better describe the invention and its embodiments, and are not intended to limit the indicated devices, elements or components to a particular orientation or to be constructed and operated in a particular orientation.

Moreover, some of the above terms may be used to indicate other meanings besides the orientation or positional relationship, for example, the term "on" may also be used to indicate some kind of attachment or connection relationship in some cases. The specific meaning of these terms in the present invention can be understood by those of ordinary skill in the art as appropriate.

Furthermore, the terms "disposed" and "connected" should be interpreted broadly. For example, "connected" may be a fixed connection, a detachable connection, or a unitary construction; can be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements or components. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

Example 1

The embodiment provides a triple-effect evaporation system for evaporating and extracting salt from coking wastewater, the structural schematic diagram of which is shown in fig. 1, and as can be seen from fig. 1, the system comprises: the system comprises a first-effect evaporation device, a second-effect evaporation device and a third-effect evaporation device, wherein the first-effect evaporation device comprises a first-effect separator 2, a first-effect heater 5 and a first-effect circulating pump 8, and the first-effect separator 2, the first-effect circulating pump 8 and the first-effect heater 5 form a circulating passage through pipelines;

the double-effect evaporation device comprises a double-effect separator 3, a double-effect heater 6 and a double-effect circulating pump 9, wherein the double-effect separator 3, the double-effect circulating pump 9 and the double-effect heater 6 form a circulating passage through a pipeline;

the triple-effect evaporation device comprises a triple-effect separator 4, a triple-effect heater 7 and a triple-effect circulating pump 10, wherein the triple-effect separator 4, the triple-effect circulating pump 10 and the triple-effect heater 7 form a circulating passage through a pipeline;

wherein the system further comprises: the system comprises a first-effect concentrated liquid pump 8, a second-effect concentrated liquid pump 9, a first cyclone 21, a magma centrifugal separation device, a gas-liquid separator 25, a main cooler 16 and an evaporation concentration condensing device; the evaporation concentration condensing device comprises a preheater 24, an evaporation condenser 1 and an evaporation cold circulating pump 23; the outlet of the circulating water tank at the bottom of the evaporative condenser 1 is respectively communicated with the water side inlet of the main cooler 16 and the water inlet of the cooling crystallizer 19 through pipelines and a concentrated water pump 26, and the water side outlet of the main cooler 16 and the water outlet of the cooling crystallizer 19 are converged and then communicated with the feed inlet of the primary effect separator 2 through pipelines;

an outlet of the raw water pump is communicated with a cold side inlet of the preheater 24 through a pipeline, a cold side outlet of the raw water pump is communicated with an inlet of a spraying device at the top of the evaporative condenser 1, and a circulating water tank at the bottom of the evaporative condenser 1 is communicated with the evaporative cold circulating pump 23 and the spraying device of the evaporative condenser 1 through pipelines to form a circulating passage;

external steam enters a high-pressure inlet of a steam jet device 15 after being subjected to pressure regulation by a steam regulating valve 14, an outlet of the steam jet device 15 is communicated with a shell pass inlet of a primary heater 5 through a pipeline, and a shell pass outlet of the primary heater 5 is communicated with a condensate water inlet of a secondary heater 6 through a pipeline; a steam outlet at the top of the primary-effect separator 2 is communicated with a steam inlet of the secondary-effect heater 6, and a shell pass outlet of the secondary-effect heater 6 is communicated with a condensed water inlet of the tertiary-effect heater 7 through a pipeline; a steam outlet at the top of the two-effect separator 3 is communicated with a steam inlet of the three-effect heater 7, a shell-side outlet of the three-effect heater 7 is communicated with the main cooler 16 through a pipeline, a steam outlet of the three-effect separator 4 is communicated with an inlet of the gas-liquid separator 25 through a pipeline, a gas outlet at the top of the gas-liquid separator 25 is communicated with an inlet of a heat exchange pipe of the evaporative condenser 1 through a pipeline, and an outlet of the heat exchange pipe is communicated with an inlet of the main cooler 16;

a feed inlet of the first-effect circulating pump 8 is communicated with an inlet of the first cyclone 21 through a first-effect concentrated liquid pump 11 by a pipeline, and a top light component outlet and a bottom heavy component outlet of the first cyclone 21 are respectively communicated with a lower feed inlet of the second-effect separator 3 and a feed inlet of the first-effect circulating pump 8 by pipelines; the feed inlet of the two-effect circulating pump 9 is communicated with the lower feed inlet of the three-effect separator 4 through a pipeline by a two-effect concentrated liquid pump 12; the feed inlet of the triple-effect circulating pump 10 is communicated with the crystal slurry centrifugal separation device through a crystal slurry extraction pump 13 through a pipeline.

In this embodiment, the centrifugal separation device for crystal slurry includes a second cyclone 22, a cooling crystallizer 19 and a centrifuge 20; a first bypass and a second bypass are respectively arranged at a feed inlet of the triple-effect circulating pump 10, the first bypass is communicated with an inlet of the second cyclone 22 through a crystal slurry extraction pump 13 by a pipeline, and a light component outlet at the top of the second cyclone 22 is communicated with the second bypass by a pipeline; wherein, the first bypass is close to the bottom outlet of the three-effect separator 4, and the second bypass is close to the feed inlet of the three-effect circulating pump 10; the design can lead the crystal mush extraction pump 13 to extract the crystal mush with higher solid content at the bottom outlet of the three-effect separator 4 for separation, and the light component with lower solid content after separation directly returns to the outlet pipeline of the three-effect separator 4 (or the feed inlet of the three-effect circulating pump 10) and then directly enters the three-effect circulating pump for reheating;

the bottom heavy component outlet of the second cyclone 22 is communicated with the inlet of the cooling crystallizer 19 through a pipeline; the outlet of the cooling crystallizer 19 is communicated with the inlet of the centrifuge 20 through a pipeline.

In this embodiment, a distilled water tank is disposed at the bottom of the main cooler 16, an outlet of the distilled water tank is communicated with a hot-side inlet of the preheater 24 through a distilled water pump 18 via a pipeline, and a hot-side outlet of the preheater 24 is communicated with a distilled water delivery pipeline.

In the embodiment, the top outlet of the main cooler 16 is communicated with a vacuum pump 17 through a pipeline so as to ensure that the vacuum gauge pressure of the system is-85 kPa to-95 kPa.

In this embodiment, a bypass interface is arranged at a top steam outlet of the two-effect separator 3, and the bypass interface is communicated with a low-pressure steam inlet of the steam ejector 15 through a pipeline.

In this embodiment, the single-effect heater 5 includes two heaters arranged in parallel.

In this embodiment, the system further comprises a pretreatment device, wherein the pretreatment device comprises a settling tank, a raw water tank and a plate-and-frame filter press; wherein, the top of the settling tank is provided with a feed inlet, the middle part is provided with an outlet, and the bottom is provided with a sludge discharge port; the outlet of the settling tank is communicated with the inlet at the top of the raw water tank through a pipeline, and the outlet at the bottom of the raw water tank is communicated with the inlet at the cold side of the preheater 24 through a raw water pump through a pipeline; the sludge discharge port is communicated with the inlet of the plate-and-frame filter press through a filter pump by a pipeline, and the filtered water outlet of the plate-and-frame filter press is communicated with the inlet at the top of the raw water tank by a pipeline.

In this embodiment, a pH detector is disposed on a side surface of the raw water tank, and a probe of the pH detector extends below a liquid level in the raw water tank to detect a pH value of the raw water.

In this embodiment, the centrifugal separation apparatus for crystal slurry further includes a mother liquid tank and a mother liquid pump, wherein a mother liquid outlet of the centrifuge 20 is communicated with an inlet of the mother liquid tank through a pipeline, and an outlet of the mother liquid tank is communicated with an inlet at the top of the settling tank through the mother liquid pump through a pipeline.

In this embodiment, the feed inlets of the first-effect separator 2, the second-effect separator 3 and the third-effect separator 4 are all located below the liquid level of each effect separator.

In this embodiment, a conductivity detector is disposed at the bottom of the main cooler 16, and a probe of the conductivity detector is extended below the liquid level in the main cooler.

In this embodiment, the cooling crystallizer 19 is a jacket structure, raw water with a temperature of about 32 ℃ is used for cooling in the jacket, and the heated raw water is sent to a lower feed inlet of the single-effect separator 2.

In this embodiment, a stirrer is disposed at the top of the cooling crystallizer 19 to prevent the crystallized material from settling and blocking the pipeline and equipment.

In this embodiment, the centrifuge 20 is a horizontal spiral decanter centrifuge.

In this embodiment, the outlet of the evaporation cold circulation pump 23 is provided with a telemetering thermometer for detecting the temperature of the externally supplied cooling water.

In this embodiment, the cooling water outlet of the gas-liquid separator 25 is communicated with the top inlet of the raw water tank through a pipeline, so as to send the cooling water separated by the gas-liquid separator 25 to the raw water tank.

In this embodiment, the distilled water pipeline of the first-effect heater 5, the distilled water pipeline of the second-effect heater 6 and the distilled water pipeline of the third-effect heater 7 are respectively provided with a U-shaped water seal to ensure that the steam pressure in the shell pass of each-effect heater is in a stable state;

wherein the water seal height of the U-shaped water seal is not less than 1.5 m.

In this embodiment, if no specific description is given, each device used in the system is a conventional device, and all devices can be obtained by commercial purchase or self-construction.

Example 2

The embodiment provides a triple-effect evaporation process for evaporating and extracting salt from coking wastewater, wherein the process is realized by using the triple-effect evaporation system for evaporating and extracting salt from coking wastewater provided in embodiment 1, and the triple-effect evaporation process comprises the following specific steps:

step one, preprocessing the coking wastewater, wherein the preprocessing comprises the following steps: settling and filtering the coking wastewater by using the pretreatment device in the embodiment 1 to obtain pretreated coking wastewater (marked as raw water) and filter residues, and carrying out coal blending treatment on the filter residues after squeezing and dewatering;

wherein the content (mass concentration) of total dissolved solids in the coking wastewater is 7-8%, and the concentration of suspended matters is 100-300 mg/L; the concentration of suspended matters in the pretreated coking wastewater is less than 30 mg/L;

step two, starting a raw water pump, carrying out heat exchange and temperature rise on the pretreated coking wastewater in a preheater, then sending the raw water subjected to heat exchange and temperature rise to the top of an evaporative condenser for spraying, continuously extracting and spraying the raw water by an evaporative cold circulating pump, carrying out heat exchange with triple-effect secondary steam in a heat exchange pipe of the evaporative condenser, heating the raw water in the heat exchange process, continuously evaporating and concentrating the raw water, and continuously extracting to obtain concentrated water, wherein the mass concentration of total dissolved solids in the concentrated water is 9% and the temperature is 20-35 ℃;

cooling the triple-effect secondary steam in the heat exchange pipe of the evaporative condenser into distilled water and a small amount of non-condensable gas, and sending the distilled water and the small amount of non-condensable gas to a main cooler for further cooling;

cooling triple-effect secondary steam in a heat exchange pipe of the evaporative condenser into distilled water and a small amount of non-condensable gas, and sending the distilled water and the small amount of non-condensable gas to a main cooler to perform heat exchange and cooling with low-temperature concentrated water produced in the evaporative condenser, wherein the temperature of the cooled non-condensable gas is less than or equal to 35 ℃, and the cooled non-condensable gas is pumped out by a vacuum pump so as to always keep the vacuum degree in a triple-effect separator at about-90 kPa; the recovered condensed water (distilled water) is collected in a distilled water tank at the bottom of the main cooler, pressurized by a distilled water pump and then enters the preheater again to exchange heat with the pretreated coking wastewater, and the produced distilled water is finally reused for replenishing water of a production system;

the triple-effect secondary steam is obtained by gas-liquid separation through a gas-liquid separator, and cooling water obtained by separation can be sent to a raw water tank of the pretreatment device for re-evaporation;

pressurizing concentrated water by a concentrated water pump, then performing heat exchange and temperature rise in a main cooler and a cooling crystallizer respectively, and sending the heated concentrated water to a one-effect separator to be used as a raw material for evaporating and extracting salt;

continuously pumping concentrated water into a first-effect heater by a first-effect circulating pump, decompressing and adjusting external steam (low-pressure waste heat steam) from an outer net by a steam adjusting valve, then entering a high-pressure inlet of a steam ejector, enabling part of secondary steam to enter a low-pressure steam inlet of the steam ejector through a pipeline, mixing the external steam and part of secondary steam in the steam ejector, enabling the obtained mixed gas to enter a shell pass of the first-effect heater for heating, controlling the tube pass temperature of the first-effect heater to be 78 ℃, enabling the temperature of the primary-effect secondary steam to be 78 ℃, enabling the concentrated water in the first-effect heater to exchange heat with the mixed gas, then entering a first-effect separator for evaporating, and generating primary-effect secondary steam and primary-effect concentrated liquid;

wherein the pressure of the mixed gas is 60kPa, and the temperature is 88 ℃;

the mass concentration of total dissolved solids in the primary concentrated solution is 12.5%;

step four, the first-effect concentrated solution is extracted by a first-effect concentrated solution pump and then is sent to a first swirler for grading treatment, after treatment, the upper layer is a low-solid-content solution, and the lower layer is high-solid-content calcium sulfate slurry; feeding the calcium sulfate slurry back to a feeding hole of the one-effect circulating pump to continuously participate in circulation; the low solid content solution enters a feed inlet of the two-effect separator and is continuously pumped in the two-effect heater by the two-effect circulating pump to exchange heat with condensed water and a small amount of non-condensable gas generated after heat exchange of the primary secondary steam and external steam in the two-effect heater, and then the condensed water and the small amount of non-condensable gas enter the two-effect separator to be evaporated to generate secondary steam and secondary concentrated solution;

wherein the temperature of the secondary steam is 66 ℃;

the mass concentration of total dissolved solids in the double-effect concentrated solution is 22.1%;

step five, the second-effect concentrated solution is extracted by a second-effect concentrated solution pump and then is sent to a feed inlet of a third-effect separator, and is continuously extracted by a third-effect circulating pump in a third-effect heater to exchange heat with part of second-effect secondary steam and condensed water generated after heat exchange in the second-effect heater and a small amount of non-condensable gas, and then the condensed water and the small amount of non-condensable gas enter the third-effect separator to be evaporated again, so that third-effect secondary steam and third-effect crystal mush are generated;

condensed water and a small amount of non-condensable gas generated after heat exchange in the triple-effect heater enter the main cooler for heat exchange and cooling after the U-shaped water seal, so that distilled water and heat are recovered; in addition, the cooling medium used for heat exchange and temperature reduction can be low-temperature concentrated water (the temperature is 20-32 ℃) produced in an evaporative condenser, the temperature of the cooled non-condensable gas is less than or equal to 35 ℃, and the cooled non-condensable gas can be pumped out by a vacuum pump so as to always keep the vacuum degree in the triple-effect separator between-85 kPa and-90 kPa; the recovered condensed water (distilled water) is collected in a distilled water tank at the bottom of the main cooler, the condensed water is pressurized by a distilled water pump and then enters a preheater for heat exchange, and the generated distilled water is finally reused for replenishing water of a production system;

wherein the mass concentration of total dissolved solids in the crystal mush is 45-55%;

the temperature of the triple-effect secondary steam is 48 ℃;

in the embodiment, the circulating flow rates of circulating fluids in the tube passes of the first-effect heater, the second-effect heater and the third-effect heater are respectively ensured to be not lower than 2m/s through the circulating pumps of all the effects so as to achieve the aim of preventing scaling;

step six, the crystal mush is extracted by a crystal mush extraction pump and then is sent to a second swirler for classification treatment, the upper layer after treatment is a low solid content solution, the lower layer is a high solid content solution, the low solid content solution returns to a feed inlet of a three-way circulating pump for continuous circulation, the high solid content solution enters a cooling crystallizer, the high solid content solution exchanges heat with low-temperature concentrated water in an interlayer of the cooling crystallizer under the stirring condition, after cooling crystallization, the temperature of the obtained outlet crystal mush is 35-45 ℃, the solid content is 30% -50%, and then the outlet crystal mush is sent to a centrifuge for centrifugal separation to obtain solid salt and mother liquor;

wherein, the cooling medium used for cooling crystallization is low-temperature concentrated water produced in an evaporative condenser;

Through the measures, in the embodiment, the COD content in the obtained triple-effect magma is less than or equal to 40000mg/L, the amount of discharged mother liquor is less than or equal to 150kg/h, and the coking solid waste salt can be stably produced; the continuous stable operation time of the system is more than 90 days; the primary heater is overhauled, obvious calcium sulfate precipitation is not found, and the operation effect is good.

The above description, only for the specific embodiments of the present invention, can not limit the scope of the practice of the present invention, so that the replacement of the equivalent components or the equivalent changes and modifications made according to the protection scope of the present invention should still belong to the scope covered by the present invention.

Claims

1. A triple-effect evaporation system for evaporating and extracting salt from coking wastewater comprises a single-effect evaporation device, a double-effect evaporation device and a triple-effect evaporation device, wherein the single-effect evaporation device comprises a single-effect separator (2), a single-effect heater (5) and a single-effect circulating pump (8) which form a circulating path; the double-effect evaporation device comprises a double-effect separator (3) forming a circulation passage, a double-effect heater (6) and a double-effect circulation pump (9); the triple-effect evaporation device comprises a triple-effect separator (4) forming a circulation passage, a triple-effect heater (7) and a triple-effect circulation pump (10);

characterized in that the system further comprises: the device comprises a first cyclone (21), a crystal slurry centrifugal separation device, a gas-liquid separator (25), a main cooler (16) and an evaporation concentration condensing device; the evaporation concentration condensing device comprises a preheater (24) and an evaporation condenser (1);

a cold side inlet of the preheater (24) is communicated with a coking wastewater pipeline, a cold side outlet of the preheater is communicated with a spraying device inlet at the top of the evaporative condenser (1), and a circulating water tank at the bottom of the evaporative condenser (1) forms a circulating passage with the evaporative cold circulating pump (23) and the spraying device of the evaporative condenser (1) through pipelines; the outlet of the circulating water tank at the bottom of the evaporative condenser (1) is also communicated with the feed inlet of the first-effect separator (2) through a pipeline;

a shell pass inlet of the primary heater (5) is communicated with a steam pipeline, and a shell pass outlet of the primary heater (5) is communicated with a condensate water inlet of the secondary heater (6) through a pipeline; a steam outlet of the primary-effect separator (2) is communicated with a steam inlet of the secondary-effect heater (6), and a shell pass outlet of the secondary-effect heater (6) is communicated with a condensed water inlet of the tertiary-effect heater (7) through a pipeline; a steam outlet of the two-effect separator (3) is communicated with a steam inlet of the three-effect heater (7), a shell side outlet of the three-effect heater (7) is communicated with the main cooler (16) through a pipeline, a steam outlet of the three-effect separator (4) is communicated with an inlet of a heat exchange pipe of the evaporative condenser (1) through the gas-liquid separator (25) through a pipeline, and an outlet of the heat exchange pipe is communicated with an inlet of the main cooler (16);

a feed inlet of the first-effect circulating pump (8) is communicated with an inlet of the first cyclone (21) through a first-effect concentrated liquid pump (11) by a pipeline, and a light component outlet and a heavy component outlet of the first cyclone (21) are respectively communicated with a feed inlet of the second-effect separator (3) and a feed inlet of the first-effect circulating pump (8) by pipelines; a feed inlet of the two-effect circulating pump (9) is communicated with a feed inlet of the three-effect separator (4) through a two-effect concentrated liquid pump (12) by a pipeline; the feed inlet of the triple-effect circulating pump (10) is communicated with the crystal slurry centrifugal separation device through a crystal slurry extraction pump (13) through a pipeline.

2. The system according to claim 1, wherein the magma centrifugal separation device comprises a second cyclone (22), a cooling crystallizer (19) and a centrifuge (20); a feed inlet of the triple-effect circulating pump (10) is communicated with an inlet of the second cyclone (22) through a crystal slurry extraction pump (13) by a pipeline, and a light component outlet and a heavy component outlet of the second cyclone (22) are respectively communicated with the feed inlet of the triple-effect circulating pump (10) and an inlet of the cooling crystallizer (19) by pipelines; the outlet of the cooling crystallizer (19) is communicated with the inlet of the centrifuge (20) through a pipeline.

3. The system according to claim 2, characterized in that the outlet of the circulating water tank at the bottom of the evaporative condenser (1) is respectively communicated with the water side inlet of the main cooler (16) and the water inlet of the cooling crystallizer (19) through pipelines and a concentrated water pump (26), and the water side outlet of the main cooler (16) and the water outlet of the cooling crystallizer (19) are converged and then communicated with the feed inlet of the single-effect separator (2) through pipelines.

4. The system according to claim 1, characterized in that the bottom of the main cooler (16) is provided with a distilled water tank, the outlet of which is connected with the hot side inlet of the preheater (24) through a distilled water pump (18) by a pipeline, and the hot side outlet of the preheater (24) is connected with a distilled water delivery pipeline.

5. The system of claim 1 or 4, characterized in that the top outlet of the main cooler (16) is connected to a vacuum pump (17) through a pipe to ensure a vacuum gauge pressure of-85 kPa to-95 kPa.

6. The system according to claim 1, characterized in that the steam pipe is provided with a steam regulating valve (14) and a steam ejector (15) in sequence.

7. The system according to claim 6, characterized in that the steam outlet of the two-effect separator (3) is provided with a bypass interface which communicates with the low-pressure steam inlet of the steam ejector (15) through a pipe.

8. A system according to claim 1, characterized in that the single effect heater (5) comprises two heaters arranged in parallel.

9. The system of claim 1 or 2, further comprising a pretreatment apparatus comprising a settling tank, a raw water tank, and a plate and frame filter press; wherein, the top of the settling tank is provided with a feed inlet, the middle part is provided with an outlet, and the bottom is provided with a sludge discharge port; the outlet of the settling tank is communicated with the inlet at the top of the raw water tank through a pipeline, and the outlet at the bottom of the raw water tank is communicated with the inlet at the cold side of the preheater (24) through a raw water pump through a pipeline; the sludge discharge port is communicated with the inlet of the plate-and-frame filter press through a filter pump by a pipeline, and the filtered water outlet of the plate-and-frame filter press is communicated with the inlet at the top of the raw water tank by a pipeline.

10. The system according to claim 9, wherein the centrifugal separation device for crystal slurry further comprises a mother liquid tank, a mother liquid pump, wherein the mother liquid outlet of the centrifuge (20) is communicated with the mother liquid tank inlet through a pipeline, and the outlet of the mother liquid tank is communicated with the inlet of the settling tank through the mother liquid pump through a pipeline.