CN112755558A - Brine evaporation and concentration system, brine evaporation and concentration process and application thereof - Google Patents
Brine evaporation and concentration system, brine evaporation and concentration process and application thereof Download PDFInfo
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- CN112755558A CN112755558A CN202011528618.7A CN202011528618A CN112755558A CN 112755558 A CN112755558 A CN 112755558A CN 202011528618 A CN202011528618 A CN 202011528618A CN 112755558 A CN112755558 A CN 112755558A
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- 238000001704 evaporation Methods 0.000 title claims abstract description 328
- 230000008020 evaporation Effects 0.000 title claims abstract description 323
- 239000012267 brine Substances 0.000 title claims abstract description 197
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 title claims abstract description 197
- 238000000034 method Methods 0.000 title claims abstract description 61
- 230000008569 process Effects 0.000 title claims abstract description 58
- 238000010438 heat treatment Methods 0.000 claims abstract description 238
- 238000009826 distribution Methods 0.000 claims abstract description 32
- 150000003839 salts Chemical class 0.000 claims abstract description 31
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 28
- 239000011552 falling film Substances 0.000 claims abstract description 10
- 239000010408 film Substances 0.000 claims abstract description 10
- 230000000694 effects Effects 0.000 claims description 119
- 238000000605 extraction Methods 0.000 claims description 24
- 238000004140 cleaning Methods 0.000 claims description 11
- 238000009833 condensation Methods 0.000 claims description 10
- 230000005494 condensation Effects 0.000 claims description 10
- 230000005484 gravity Effects 0.000 claims description 10
- 229920006395 saturated elastomer Polymers 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 6
- 238000003780 insertion Methods 0.000 claims description 4
- 230000037431 insertion Effects 0.000 claims description 4
- 239000007791 liquid phase Substances 0.000 claims description 4
- 239000012071 phase Substances 0.000 claims description 4
- 239000007921 spray Substances 0.000 claims description 4
- 239000011148 porous material Substances 0.000 claims description 2
- 238000007599 discharging Methods 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 9
- 238000005265 energy consumption Methods 0.000 abstract description 3
- 238000011084 recovery Methods 0.000 abstract description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- 239000007789 gas Substances 0.000 description 11
- 238000005868 electrolysis reaction Methods 0.000 description 10
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 7
- 238000002425 crystallisation Methods 0.000 description 7
- 230000008025 crystallization Effects 0.000 description 7
- 239000010936 titanium Substances 0.000 description 7
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 6
- 238000004064 recycling Methods 0.000 description 5
- 239000012266 salt solution Substances 0.000 description 5
- 229910052719 titanium Inorganic materials 0.000 description 5
- 238000006298 dechlorination reaction Methods 0.000 description 4
- 239000011780 sodium chloride Substances 0.000 description 4
- 235000011121 sodium hydroxide Nutrition 0.000 description 4
- 239000000463 material Substances 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 229910000851 Alloy steel Inorganic materials 0.000 description 2
- 229910001200 Ferrotitanium Inorganic materials 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000001739 density measurement Methods 0.000 description 1
- 238000010612 desalination reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000005514 two-phase flow Effects 0.000 description 1
- 239000006200 vaporizer Substances 0.000 description 1
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/26—Multiple-effect evaporating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/22—Evaporating by bringing a thin layer of the liquid into contact with a heated surface
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/30—Accessories for evaporators ; Constructional details thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D1/00—Evaporating
- B01D1/30—Accessories for evaporators ; Constructional details thereof
- B01D1/305—Demister (vapour-liquid separation)
-
- 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
-
- 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
- C02F1/08—Thin film evaporation
Abstract
The invention provides a brine evaporation and concentration system, a brine evaporation and concentration process and application thereof, wherein the brine evaporation and concentration system comprises a preheating subsystem, an evaporation subsystem and a raw steam subsystem; the evaporation subsystem comprises a condensate tank, an I-effect evaporation subsystem, a II-effect evaporation subsystem and an N-effect evaporation subsystem, wherein the I-effect evaporation subsystem and the II-effect evaporation subsystem are sequentially connected in series, and each of the I-effect evaporation subsystem and the II-effect evaporation subsystem respectively and independently comprises an evaporation chamber, a heating chamber, a pump and a corresponding pipeline in corresponding levels; the I-effect to N-1-effect evaporation chambers are all falling-film evaporators, and the N-effect evaporation chamber is a forced circulation rising-film evaporator. The brine evaporation and concentration system has the advantages of low manufacturing cost, safe operation, wide applicable light brine concentration range, uniform effective temperature difference distribution among the evaporation subsystems, good system heat exchange and stable working condition. The process does not need a salt dissolving process, and solves the problems that the existing light salt water recovery system has high energy consumption and cannot effectively utilize the higher water temperature and salt concentration of the light salt water.
Description
Technical Field
The invention belongs to the technical field of brine treatment, and particularly relates to a brine evaporation and concentration system and a brine evaporation and concentration process.
Background
In the field of caustic soda production, more than 500 chlor-alkali producers are shared worldwide, and the total caustic soda production can be nearly 9500 million t/a. In recent years, the global capacity of the world caustic soda industry has small overall change, and newly increased capacity is concentrated in developing countries such as China, India, middle east and the like. In addition to the large power consumption of ion membrane electrolysis, another major production cost is the price of the raw brine.
For the domestic chlor-alkali industry, the concentration of sodium chloride in the dilute brine discharged from the ion membrane electrolytic cell is 200-220 g/L, the temperature is 80-90 ℃, after dechlorination, the temperature of the dilute brine is 70-80 ℃, the main treatment mode of dechlorination of the dilute brine is that part of the dilute brine exchanges heat with the concentrated brine after salt dissolving, then the dilute brine is cooled by circulating water and enters a freezing denitration system, the denitrated or non-denitrated dilute brine is mixed with the replenishing water of a production system and then enters a salt dissolving system, solid salt is added again to prepare sodium chloride solution (300-320 g/L), and then the concentrated brine for electrolysis is obtained through primary brine and secondary brine treatment. For the traditional process, solid salt needs to be added, the refining treatment is carried out, the cost is increased, the loss is caused, particularly, in enterprises using brine as a raw material, the solid salt needs to be additionally purchased to meet the use requirement, and the production cost is greatly increased. In countries such as the middle east, possess more sea water desalination device, the enterprise that uses brine as the raw materials is many, if the facility of new-built electrolysis production caustic soda uses neotype light salt solution evaporation concentration system, retrieves and recycles light salt solution and carries out circulation electrolysis, need not set up processes such as salt dissolving system, can reduce raw materials salt solution cost to minimumly.
Disclosure of Invention
In view of the problems in the prior art, the present invention provides a brine evaporation and concentration system, a brine evaporation and concentration process using the brine evaporation and concentration system, and applications of the brine evaporation and concentration system and the brine evaporation and concentration process in the technical field of brine evaporation and concentration. The invention applies the brine evaporation and concentration system with economic cost, reasonable structure, simple volume and high safety performance to the brine evaporation and concentration process, thereby scientifically planning the brine evaporation and concentration process, reducing consumption and improving efficiency.
The invention provides a brine evaporation and concentration system in a first aspect, which comprises a preheating subsystem, an evaporation subsystem and a steam subsystem; the evaporation subsystem comprises a condensate tank, an I-effect evaporation subsystem, a II-effect evaporation subsystem and an N-effect evaporation subsystem, wherein the I-effect evaporation subsystem and the II-effect evaporation subsystem are sequentially connected in series, and each of the I-effect evaporation subsystem and the II-effect evaporation subsystem respectively and independently comprises an evaporation chamber, a heating chamber, a pump and a corresponding pipeline in corresponding levels; the I-effect to N-1-effect evaporation chambers are all falling-film evaporators, and the N-effect evaporation chamber is a forced circulation rising-film evaporator;
in the evaporation subsystems from the effect I to the effect N-1, a bottom discharge hole of the evaporation chamber is connected with a top feed hole of the heating chamber through a pump, and a bottom discharge hole of the heating chamber is connected with a lower feed hole of the evaporation chamber; one branch of the discharge hole of the pump with the first effect is connected with the top feed inlet of the heating chamber with the second effect; a discharge port at the top of the front-effect evaporation chamber is connected with a shell pass feed inlet of the rear-effect heating chamber;
in the Nth-effect evaporation subsystem, a discharge port at the top of the evaporation chamber is connected with a vacuum system; a discharge port at the lower part of the evaporation chamber is connected with a feed port at the bottom of the heating chamber through a pump, and a discharge port at the top of the heating chamber is connected with a feed port of the evaporation chamber; a product extraction outlet is arranged on a connecting pipeline of a lower discharge port of the evaporation chamber and a bottom feed inlet of the heating chamber, and the product extraction outlet is connected with a product extraction pipeline; a branch of a discharge hole of the N-1 th-effect pump is connected with a feed hole of the N-1 th-effect pump, and a discharge hole at the top of the N-1 th-effect evaporation chamber is connected with a shell pass feed hole of the N-1 th-effect heating chamber;
in the second-effect evaporation subsystem to the Nth-effect evaporation subsystem, a shell pass discharge port of each-effect heating chamber is connected with a condensate tank; optionally, a shell pass discharge port of the first-effect heating chamber is connected with a condensate tank;
optionally, the shell side of each effect heating chamber further comprises a non-condensable gas outlet, and the non-condensable gas outlets of the effect heating chambers are connected with the vacuum system respectively and independently;
the preheating subsystem comprises a plurality of preheaters which are sequentially connected in series, and a discharge hole of the preheating subsystem is connected with a top feed inlet of the I-effect heating chamber;
a raw steam outlet of the raw steam subsystem is connected with a shell pass feed inlet of the I-effect heating chamber;
n is a positive integer of 2 or more, preferably N is a positive integer of 3 to 8, and may be 3, 4, 5, 6, 7 and 8, with N being most preferably 5.
In some preferred embodiments of the brine evaporation and concentration system according to the present invention, in the nth effect evaporation subsystem, the product extraction line connected to the product extraction port further includes a built-in density measurement instrument and a control valve matched therewith, and an unqualified brine return line is connected between the product extraction line and the pump.
In some preferred embodiments of the brine evaporation and concentration system according to the present invention, the steam subsystem further includes a raw steam condensate tank, a raw steam outlet is connected to a raw steam distribution pipe in the raw steam condensate tank, a gas phase outlet of the raw steam condensate tank is connected to a shell side feed inlet of the I-effect heating chamber, and a liquid phase outlet of the raw steam condensate tank is connected to an inlet of any preheater in the preheating subsystem.
In some preferred embodiments of the brine evaporation and concentration system according to the invention, one branch of the top discharge port of each effect evaporation chamber is independently connected to the steam feed port of any preheater in the evaporation subsystem.
In some preferred embodiments of the brine evaporative concentration system according to the invention, the condensate tank outlet is connected to a second condensate pump.
In some preferred embodiments of the brine evaporative concentration system according to the invention, the condensate tank is connected to the shell side pressure of the nth effect heater.
In some preferred embodiments of the brine evaporation and concentration system according to the invention, a liquid level control device is arranged in the front N-1-effect evaporation subsystem, and a pipeline connecting the front-effect pump and the top feed inlet of the rear-effect heating chamber and the rear-effect evaporation chamber.
In some preferred embodiments of the brine evaporation and concentration system according to the present invention, a product pump is disposed on the product withdrawal line, and preferably, the product pump is provided with a variable frequency control device.
In some preferred embodiments of the brine evaporation and concentration system according to the present invention, the raw steam distribution pipe is installed inside the condensing tank in an inner insertion pipe manner, and the pipe wall is provided with distribution holes, preferably, the hole diameter of the distribution holes is Φ 5 to Φ 50, more preferably, Φ 20 to Φ 50.
In some preferred embodiments of the brine evaporative concentration system according to the present invention, each of the effective heating chambers is independently a shell-and-tube heat exchanger, and includes a barrel, a heat exchange tube bundle, and a demister, the demister being located at the top inside the barrel. The demisting device is conventional equipment in the field and comprises a thin plate and a silk screen, wherein the thin plate is used for fixing the silk screen so as to achieve a demisting effect.
In some preferred embodiments of the brine evaporative concentration system according to the present invention, the demister further comprises a cleaning nozzle adapted to spray a cleaning spray having a cone angle of 50 ° to 150 °, preferably 90 ° to 120 °. Through setting up clean nozzle, realized defogging device's self-cleaning function.
In some preferred embodiments of the brine evaporation and concentration system according to the present invention, a distributor or a distribution plate is disposed on the top of the heat exchange tube bundle of each effective heating chamber, so that brine can be uniformly distributed to each heat exchange tube; preferably, the distributor or distribution tray is of the grid or sieve plate type.
In some preferred embodiments of the brine evaporation and concentration system according to the invention, the distributor or distribution plate has a mesh size of Φ 5 to Φ 50.
In some preferred embodiments of the brine evaporative concentration system according to the present invention, the effective heating chambers are each independently made of titanium or alloy steel; wherein, the heat exchange tube bundle of the heating chamber is preferably made of titanium.
In some preferred embodiments of the brine evaporation and concentration system according to the invention, the inner tube bundle of the efficient heating chamber is a single pass, and the length-to-diameter ratio of the tube bundle is 50 to 500, preferably 100 to 400, and more preferably 200 to 300.
In some preferred embodiments of the brine evaporation and concentration system according to the present invention, the pipeline connected between the devices is made of titanium.
In some preferred embodiments of the brine evaporative concentration system according to the present invention, the connections between the devices are flange and bolt connections.
The invention provides a brine evaporation concentration process in a second aspect, which comprises the following steps:
(1) the light salt water enters the I-effect evaporation subsystem and the II-effect evaporation subsystem in sequence after being preheated until the N-effect evaporation subsystem is concentrated; in each effect evaporation subsystem, the preheated dilute brine enters an I-effect evaporation chamber for evaporation after being heated by a tube pass of the I-effect heating chamber; the pre-concentrated light salt water leaves the I-effect evaporation chamber through the I-effect pump, flows to the II-effect evaporation chamber and is further evaporated and concentrated; repeating the same evaporation process as the I-effect evaporation chamber in the II-effect evaporation chamber, the III-effect evaporation chamber and the N-effect evaporation chamber until the salt water reaches the required concentration;
(2) raw steam from a battery compartment enters a shell pass of the I-effect heating chamber to heat the dilute brine, and the temperature of the dilute brine preheated by the preheating subsystem is close to the operating temperature of the I-effect evaporation chamber;
(3) the method comprises the following steps that (1) the I-effect evaporation chamber is communicated with the N-effect evaporation chamber, steam obtained by evaporating the light salt water in the previous effect evaporation chamber is used as a heat source of the next effect heating chamber and enters the shell pass of the next effect heating chamber, and steam in the Nth effect evaporation chamber is discharged out of a salt water evaporation and concentration system;
(4) the strong brine product is sent to a battery compartment after being evaporated by the N-effect evaporation chamber;
(5) the condensate tank collects all the condensate from the II-effect heating chambers to the N-effect heating chambers and optional condensate of the I-effect heating chambers, and the condensate is pumped to the battery limits through the second condensate.
In some preferred embodiments of the evaporative concentration process of brine according to the present invention, the weak brine is fed concurrently with the heating medium of the preheating sub-system.
In some preferred embodiments of the brine evaporation and concentration process according to the present invention, the raw steam firstly enters the raw steam condensation tank through a distribution pipe below the raw steam condensation tank, and directly contacts with the condensed water from the shell side discharge port of the I-effect heating chamber, the raw steam is cooled and depressurized in the raw steam condensation tank to reach saturation, and the saturated steam is directly fed into the shell side feed port of the I-effect heating chamber.
In some preferred embodiments of the brine evaporative concentration process according to the present invention, the steam heating the I-effect heating chamber becomes a condensate after releasing latent heat on the shell side, and the condensate leaves the bottom of the I-effect heating chamber and flows into a raw steam condensate tank.
In some preferred embodiments of the brine evaporative concentration process according to the present invention, the condensate is continuously withdrawn from the raw steam condensate tank by a first condensate pump to a first preheater of the preheating sub-system, and the preheated dilute brine is sent to the battery compartment.
In some preferred embodiments of the brine evaporation and concentration process according to the invention, the product concentration is controlled by a density measuring instrument and a control valve which are arranged in a recirculation pipe connecting the N-effect evaporation chamber and the N-effect heating chamber, and when the concentrated brine is unqualified, the control valve is closed, and the concentrated brine returns to the Nth effect evaporation subsystem; when the strong brine is qualified, the control valve is opened, and the strong brine is sent to a boundary area.
In some preferred embodiments of the brine evaporation and concentration process according to the invention, a part of the condensate in the condensate tank is flashed into steam in the condensate tank, and the steam enters the N-effect heating chamber.
In some preferred embodiments of the brine evaporation and concentration process according to the invention, part of the steam generated from the effect-I evaporation chamber is used as heating steam of the effect-III preheater, and the rest part of the steam is used as heating steam to enter the effect-II heating chamber, and preferably condensate in the effect-II heating chamber enters the shell side of the effect-III heating chamber through gravity flow; more preferably, the flow ratio of the heating steam used as the third preheater to the heating steam used as the II-effect heating chamber is (0.2-3): 1, and more preferably (0.5-1): 1.
In some preferred embodiments of the brine evaporation and concentration process according to the invention, part of the steam generated from the second-effect evaporation chamber is used as heating steam of the second-effect preheater, and the rest part of the steam is used as heating steam to enter the third-effect heating chamber, and preferably condensate in the third-effect heating chamber enters the shell side of the IV-effect heating chamber through gravity flow; more preferably, the flow ratio of the heating steam used as the second preheater to the heating steam used as the third-effect heating chamber is (0.2-3): 1, and more preferably (0.5-1): 1.
In some preferred embodiments of the brine evaporative concentration process according to the present invention, the brine evaporative concentration system utilized comprises a preheating subsystem, an evaporation subsystem and a raw steam subsystem; the evaporation subsystem comprises a condensate tank, an I-effect evaporation subsystem, a II-effect evaporation subsystem and an N-effect evaporation subsystem, wherein the I-effect evaporation subsystem and the II-effect evaporation subsystem are sequentially connected in series, and each of the I-effect evaporation subsystem and the II-effect evaporation subsystem respectively and independently comprises an evaporation chamber, a heating chamber, a pump and a corresponding pipeline in corresponding levels; the I-effect to N-1-effect evaporation chambers are all falling-film evaporators, and the N-effect evaporation chamber is a forced circulation rising-film evaporator;
in the evaporation subsystems from the I effect to the N-1 effect, a bottom discharge hole of the evaporation chamber is connected with a top feed hole of the heating chamber through a pump, and a bottom discharge hole of the heating chamber is connected with a lower feed hole of the evaporation chamber; one branch of the discharge hole of the pump with the first effect is connected with the top feed inlet of the heating chamber with the second effect; a discharge port at the top of the front-effect evaporation chamber is connected with a shell pass feed inlet of the rear-effect heating chamber;
in the Nth-effect evaporation subsystem, a discharge port at the top of the evaporation chamber is connected with a vacuum system; a discharge port at the lower part of the evaporation chamber is connected with a feed port at the bottom of the heating chamber through a pump, and a discharge port at the top of the heating chamber is connected with a feed port of the evaporation chamber; a product extraction outlet is arranged on a connecting pipeline of a lower discharge port of the evaporation chamber and a bottom feed inlet of the heating chamber, and the product extraction outlet is connected with a product extraction pipeline; a branch of a discharge hole of the N-1 th-effect pump is connected with a feed hole of the N-1 th-effect pump, and a discharge hole at the top of the N-1 th-effect evaporation chamber is connected with a shell pass feed hole of the N-1 th-effect heating chamber;
in the second-effect evaporation subsystem to the Nth-effect evaporation subsystem, a shell pass discharge port of each effect heating chamber is connected with a condensate tank; optionally, a shell pass discharge port of the first-effect heating chamber is connected with a condensate tank;
optionally, the shell side of each effect heating chamber further comprises a non-condensable gas outlet, and the non-condensable gas outlets of the effect heating chambers are connected with the vacuum system respectively and independently;
the preheating subsystem comprises a plurality of preheaters which are sequentially connected in series, and a discharge hole of the preheating subsystem is connected with a top feed inlet of the I-effect heating chamber;
a raw steam outlet of the raw steam subsystem is connected with a shell pass feed inlet of the I-effect heating chamber;
n is a positive integer of 2 or more, preferably N is a positive integer of 3 to 8, and more preferably N-5.
In some preferred embodiments of the brine evaporation and concentration process according to the present invention, in the nth effect evaporation subsystem, the product extraction line connected to the product extraction port further includes a built-in density measuring instrument and a control valve matched with the built-in density measuring instrument, and an unqualified brine return line is connected between the product extraction line and the pump.
In some preferred embodiments of the brine evaporation and concentration process according to the present invention, the raw steam subsystem further includes a steam condensate tank, a raw steam outlet is connected to a raw steam distribution pipe in the steam condensate tank, a gas phase outlet of the steam condensate tank is connected to the shell side feed inlet of the I-effect heating chamber, and a liquid phase outlet of the steam condensate tank is connected to an inlet of any preheater in the preheating subsystem.
In some preferred embodiments of the brine evaporation and concentration process according to the invention, one branch of the top discharge port of each effect evaporation chamber is independently connected to the steam feed port of any preheater in the evaporation subsystem.
In some preferred embodiments of the brine evaporative concentration process according to the invention, the condensate tank outlet is connected to a second condensate pump.
In some preferred embodiments of the brine evaporative concentration process according to the present invention, the condensate tank is connected to the shell side pressure of the nth effect heater.
In some preferred embodiments of the brine evaporation and concentration process according to the invention, a liquid level control device is arranged in the front N-1-effect evaporation subsystem, and a pipeline connecting the front-effect pump and the top feed inlet of the rear-effect heating chamber and the rear-effect evaporation chamber.
In some preferred embodiments of the brine evaporation and concentration process according to the present invention, a product pump is disposed on the product withdrawal line, and preferably the product pump is equipped with a variable frequency control device.
In some preferred embodiments of the brine evaporation and concentration process according to the present invention, the raw steam distribution pipe is installed inside the condensation tank in an inner insertion pipe manner, and the pipe wall is provided with distribution holes, preferably, the hole diameter of the distribution holes is Φ 5 to Φ 50, more preferably, Φ 20 to Φ 50.
In some preferred embodiments of the brine evaporative concentration process according to the present invention, each of the effective heating chambers is independently a shell-and-tube heat exchanger, and comprises a cylinder, a heat exchange tube bundle and a demister, and the demister is positioned at the top inside the cylinder. The demisting device is conventional equipment in the field and comprises a thin plate and a silk screen, wherein the thin plate is used for fixing the silk screen so as to achieve a demisting effect.
In some preferred embodiments of the brine evaporative concentration process according to the present invention, the demisting apparatus further comprises a cleaning nozzle adapted to spray a cleaning nozzle having a cone angle of 50 ° to 150 °, preferably 90 ° to 120 °. Through setting up clean nozzle, realized that the defogging device has the self-cleaning function.
In some preferred embodiments of the brine evaporation and concentration process according to the present invention, a distributor or a distribution plate is disposed on the top of the heat exchange tube bundle of each effect heating chamber, so that brine can be uniformly distributed to each heat exchange tube; preferably, the distributor or distribution tray is of the grid or sieve plate type.
In some preferred embodiments of the brine evaporation and concentration process according to the present invention, the size of the mesh of the distributor or distribution plate is from Φ 5 to Φ 50.
In some preferred embodiments of the brine evaporative concentration process according to the present invention, the respective effective heating chambers are each independently made of titanium or alloy steel; wherein, the heat exchange tube bundle of the heating chamber is preferably made of titanium.
In some preferred embodiments of the brine evaporation and concentration process according to the present invention, the inner tube bundle of the efficient heating chamber is a single pass, and the length-to-diameter ratio of the tube bundle is 50 to 500, preferably 100 to 400, and more preferably 200 to 300.
In some preferred embodiments of the brine evaporation and concentration process according to the present invention, the pipeline connected between the devices is made of titanium material.
In some preferred embodiments of the brine evaporative concentration process according to the present invention, the connections between the devices are flange and bolt connections.
The third aspect of the invention provides the application of the brine evaporation and concentration system and the brine evaporation and concentration process in the field of brine concentration treatment.
The invention provides the brine evaporation and concentration system and the application of the brine evaporation and concentration process in the concentration treatment of the electrolytic dechlorination dilute brine, wherein the concentration of the electrolytic dechlorination dilute brine is 100 g/L-220 g/L, and preferably the brine evaporation and concentration system comprises a five-effect evaporation subsystem.
The invention has the advantages that at least the following aspects are achieved:
1. the brine evaporation and concentration system has the advantages of low manufacturing cost, safe operation, wide applicable light brine concentration range, uniform effective temperature difference distribution among the evaporation subsystems, good system heat exchange and stable working condition.
2. The brine evaporation and concentration process disclosed by the invention does not need a salt melting process, solves the problems that the existing dilute brine recovery system is high in energy consumption and cannot effectively utilize the higher water temperature and salt concentration of the dilute brine, and improves the utilization rate of the dilute brine.
3. The brine evaporation and concentration process can fully improve the steam efficiency, reduce consumption and improve efficiency. By utilizing the secondary steam for many times, the energy consumption of unit products can be effectively reduced, and the energy is saved.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
FIGS. 1 and 2 are schematic diagrams of the process flow of evaporative concentration and recycling of five-effect and three-effect light salt water according to examples 1-2; wherein the content of the first and second substances,
EV1-I effect evaporation chamber; EV2-II effect evaporation chamber; EV3-III effect evaporation chamber; EV4-IV effect evaporation chamber; EV5-V effect evaporation chamber;
HE1-I effect heating chamber; HE2-II effect heating chamber; HE3-III effect heating chamber; HE4-IV effect heating chamber; HE5-V effect heating chamber;
P01-I effect pump; a P02-II effect pump; a P03-III effect pump; a P04-IV effect pump; P05-V effect pump; p06-product pump; p07 — first condensate pump; p08 — second condensate pump;
RP 1-first recycle line; RP 2-second recycle line; RP 3-third recycle line; RP 4-fourth recycle line; RP 5-fifth recycle line;
PH 1-first preheater; PH 2-second preheater; PH 3-third preheater;
CT 1-raw steam condensate tank; CT 2-gel tank;
1-weak brine line entering an I-effect preheater PH 1;
2-weak brine line entering II effect preheater PH 2;
3-weak brine line to effect III preheater PH 3;
4-weak brine line to effect I vaporizer EV 1;
a first recirculation pipe RP1 of the weak brine of the 5-effect evaporation chamber EV 1;
a weak brine pipeline from the 6-I effect evaporation chamber EV1 to the II effect evaporation chamber EV 2;
a second recycle pipe RP2 for weak brine of the 7-II effect evaporator EV 2;
a weak brine pipeline from the 8-II effect evaporation chamber EV2 to the III effect evaporation chamber EV 3;
a 9-III effect evaporator EV3, a weak brine third recirculation pipe RP 3;
a weak brine line from the 10-III effect evaporation chamber EV3 to the IV effect evaporation chamber EV 4;
11-IV effect evaporator EV4, weak brine fourth recirculation pipe RP 4;
a weak brine line from the 12-IV effect evaporation chamber EV4 to the V effect evaporation chamber EV 5;
a fifth recycle pipe RP5 for weak brine from the 13-V effect evaporator EV 5;
14-product extraction lines;
15-unqualified strong brine reflux pipeline;
16-forced circulation pump return line;
17-vacuum system line;
18-condensate line from first condensate pump P07 to I-effect preheater PH 1;
a condensate line from the 19-effect preheater PH1 to battery limits;
20-a raw steam line from the battery limits;
21-effect heating chamber HE1 condensate line;
22-a saturated steam pipeline which enters an I-effect evaporation chamber EV1 after temperature reduction;
heating steam lines of the 23-I-effect evaporation chamber EV1 to the II-effect evaporation chamber EV 2;
heating steam lines of the 24-II-effect evaporation chambers EV2 to the III-effect evaporation chamber EV 3;
heating steam lines of the 25-III-effect evaporation chambers EV3 to IV-effect evaporation chamber EV 4;
heating steam lines of the 26-IV-effect evaporation chamber EV4 to the V-effect evaporation chamber EV 5;
a condensate line of the 27-II effect heating chamber EV 2;
a condensate line of the 28-III effect heating chamber EV 3;
a condensate line of the 29-IV effect heating chamber EV 4;
30-flash vapor line of second condensate tank CT 2;
a condensate line of the 31-V effect heating chamber EV 5;
32-second condensate tank CT2 to battery limits condensate line;
CV-control valve.
FIG. 3 is a schematic structural view of a demister and an automatic cleaning apparatus according to embodiments 1 to 2; wherein, 33-upper nozzle; 34-a wire mesh; 35-a sheet; 36-lower nozzle;
FIG. 4 is a schematic view of the process flow of evaporating, concentrating and recycling triple-effect weak brine in example 2.
Detailed Description
The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited to the following description.
The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available from commercial sources.
The invention relates to a process for producing strong brine for circular electrolysis by utilizing a dilute brine evaporation concentration device, which is suitable for the transformation of newly-built factories and old factories, can economically increase the yield of the strong brine, and greatly reduces the electrolysis cost of the whole ion membrane. The process of evaporative concentration of dilute brine according to the present invention is further illustrated below with reference to specific examples. For convenience of description, the device of the invention omits the conventional valve on the pipeline, the conventional pipe orifice, manhole, instrument interface, support and other accessories on the storage tank, and the skilled person in the industry can design the device according to the requirement. Further modifications and improvements may be made by those skilled in the art, such as changing the feed metering manner, adjusting the specification of the nozzle of the cryogenic heat recovery device, and increasing the number of interfaces, and all such modifications, adjustments, and improvements should be considered as within the scope of the present invention.
[ example 1 ]
The system that this embodiment adopted is five effect evaporation concentration systems, includes: the system comprises a preheating subsystem, an evaporation subsystem and a raw steam subsystem; the evaporation subsystem comprises a condensate tank, an I-effect evaporation subsystem and an II-effect evaporation subsystem which are sequentially connected in series, and the evaporation subsystems reach a V-effect evaporation subsystem, and each evaporation subsystem independently comprises an evaporation chamber, a heating chamber, a pump and a corresponding pipeline in corresponding levels; the first-effect to the fourth-effect evaporation chambers are all falling-film evaporators, and the V-effect evaporation chamber is a forced circulation rising-film evaporator.
In the evaporation subsystems of the effects I to IV, a bottom discharge hole of an evaporation chamber is connected with a top feed inlet of a heating chamber through a recirculation pipe by a pump, and a bottom discharge hole of the heating chamber is connected with a lower feed inlet of the evaporation chamber; one branch of the discharge hole of the pump with the first effect is connected with the top feed inlet of the heating chamber with the second effect; the top discharge hole of the previous effect evaporation chamber is connected with the shell pass feed inlet of the next effect heating chamber. A pipeline connecting the top feed inlets of the front effect pump and the rear effect heating chamber and the rear effect evaporation chamber are provided with a liquid level control device.
In the V-effect evaporation subsystem, a discharge port at the top of a V-effect evaporation chamber EV5 is connected with a vacuum system through a vacuum system pipeline 17; the lower discharge port of the V-effect evaporation chamber EV5 is connected with the bottom feed inlet of the V-effect heating chamber HE5 through a fifth recirculation pipe RP5 via a V-effect pump P05, the fifth recirculation pipe RP5 is provided with a product extraction port, the product extraction port is connected with a product extraction pipeline 14, and the product extraction pipeline 14 is provided with a product pump P06. A discharge port at the top of the V-effect heating chamber HE5 is connected with a feed port of the V-effect evaporation chamber EV5 through a fifth recirculation pipe RP5, and a density measuring instrument is arranged in a passage of the fifth recirculation pipe RP 5; one branch of the discharge hole of the IV-effect pump P04 is connected with the feed hole of the V-effect pump P05, and the discharge hole at the top of the IV-effect evaporation chamber EV4 is connected with the shell side feed hole of the V-effect heating chamber HE 5. The condensate tank CT2 is connected with the shell side pressure of the V-effect heating chamber HE 5. Wherein a density measuring instrument is built in the fifth recycling pipe RP5 for obtaining a monitored value of the product. In order to reduce the unqualified brine amount to the minimum during the start-up or load change, an additional control valve CV is also arranged on the strong brine return pipeline 15, if the strong brine has unqualified phenomena such as too low density and the like, the control valve CV on the product extraction pipeline is slowly closed, and the strong brine returns to the fifth-effect evaporation chamber EV5 through the unqualified strong brine return pipeline 15; when the density of the strong brine is close to a normal set value, a control valve CV on a product extraction pipeline is slowly opened, and the strong brine is sent to a boundary area.
In the second-effect evaporation subsystem to the V-effect evaporation subsystem, a shell pass discharge port of each effect heating chamber is connected with a condensate tank CT 2; the shell side of each effect heating chamber also comprises a non-condensable gas outlet respectively and independently, and the non-condensable gas outlets are respectively and independently connected with a vacuum system.
The preheating subsystem comprises a first preheater PH1, a second preheater PH2 and a third preheater PH3 which are sequentially connected in series, and a discharge hole of the third preheater PH3 is connected with a top feed hole of the I-effect heating chamber HE 1.
One branch of a discharge port at the top of the I-effect evaporation chamber EV1 is connected with a heating medium inlet of a third preheater PH3, and one branch of a discharge port at the top of the II-effect evaporation chamber EV2 is connected with a heating medium inlet of a second preheater PH 2. One branch of a heating medium outlet of the third preheater PH3 is connected with a shell side feed inlet of an II-effect heating chamber HE2, and the other branch is connected with a vacuum system. One branch of a heating medium outlet of the II preheater PH2 is connected with a shell side feed inlet of an III-effect heating chamber HE3, and the other branch is connected with a vacuum system.
Each effect heating chamber is shell-and-tube heat exchanger independently, includes barrel, heat exchange tube bank and defogging device, and the defogging device is located the top in the barrel. As shown in fig. 3, the defogging device is composed of a thin plate 35 and a screen 34, and further comprises matched cleaning nozzles, namely an upper nozzle 33 and a lower nozzle 36, wherein the cone angle of the spraying range of the upper nozzle 33 is 120 degrees, and the cone angle of the spraying range of the lower nozzle 36 is 90 degrees. The cleaning nozzle of the demisting device can clean the demister and the evaporator wall regularly.
The top of the heat exchange tube bundle is provided with a sieve plate type distributor, and the sieve pore size of the distributor is phi 50. The tube bundles in the heating chambers are all single-pass, and the length-diameter ratio of the tube bundles is 200.
The raw steam outlet of the raw steam subsystem is connected with a raw steam distribution pipe in a raw steam condensate tank CT1, the gas phase outlet of the raw steam condensate tank CT1 is connected with the shell side feed inlet of an I-effect heating chamber HE1, the liquid phase outlet of the raw steam condensate tank CT1 is connected with the heating medium inlet of an I-preheater PH1 in the preheating subsystem through a first condensate pump P07, and a condensate pipeline from the I-effect preheater PH1 to a boundary region, which is connected with the heating medium outlet of the I-preheater PH1, leads to a boiler room.
The raw steam distribution pipe is arranged inside the condensing tank in an inner insertion pipe mode, as shown in fig. 2, the pipe wall of the raw steam distribution pipe is provided with distribution holes, and the aperture of each distribution hole is phi 25.
In the five-effect evaporation concentration system, the brine pipeline is made of titanium materials, and all connections are connected by flanges and bolts.
The technological process of five-effect light salt water evaporation concentration and recycling comprises the following specific steps:
(1) the flow rate of the fresh brine from the electrolysis system is 110.5t/h, the temperature is 75 ℃, the concentration is 18.80 wt%, the fresh brine is preheated by a first preheater PH1, a second preheater PH2 and a third preheater PH3 in sequence, and then the fresh brine and the steam are fed in a parallel flow manner and are sent to the tube side of an I-effect heating chamber HE 1; the weak brine is fed co-currently with the heating steam in the preheater. Wherein the outlet temperatures of the first preheater PH1, the second preheater PH2 and the third preheater PH3 are 78.1 deg.C, 92.5 deg.C and 104 deg.C, respectively.
(2) Saturated steam from a raw steam condensing tank CT1 enters an I-effect heating chamber EV1, and the flow rate of the saturated steam is 7.30t/h, the temperature is 126 ℃, and the pressure is 136kPag, and the weak saline water in an I-effect evaporation chamber EV1 is heated. Steam (flow rate of 5.38t/h, temperature of 114 ℃ and pressure of 34kPag) generated by the heated weak brine enters the II-effect heating chamber HE2 as a heating source of the II-effect evaporation chamber EV2, by analogy, steam (flow rate of 5.24t/h, temperature of 103 ℃ and pressure of-11 kPag) generated by the II-effect evaporation chamber EV2 enters the III-effect heating chamber HE3, steam (flow rate of 4.60t/h, temperature of 91 ℃ and pressure of-47 kPag) generated by the III-effect evaporation chamber EV3 enters the IV-effect heating chamber HE4, steam (flow rate of 7.13t/h, temperature of 74.8 ℃ and pressure of-71 kPag) generated by the IV-effect evaporation chamber EV4 enters the V-effect heating chamber HE5, steam (flow rate of 9.34t/h, temperature of 59 ℃ and pressure of-86 kPag) generated by the V-effect evaporation chamber EV5 directly enters a vacuum system, and condensed inert gases and/or non-condensable gases are removed through the vacuum system.
(3) The weak brine which is preheated by the first preheater PH1, the second preheater PH2 and the third preheater PH3 is 104 ℃, is close to the operating temperature of the I-effect evaporation chamber EV1 and is 114 ℃, enters the I-effect evaporation chamber EV1 through the first recirculation pipe RP1 and the tube pass of the I-effect heating chamber HE1, and controls the liquid level of the I-effect evaporation chamber EV1 through flow control. The weak brine heated by the I-effect heating chamber HE1 is evaporated in the I-effect evaporation chamber, and the salt concentration of the weak brine is increased to 19.73 wt%. The pre-concentrated weak brine leaves the I-effect evaporation chamber EV1 through an I-effect pump P01 and flows to the II-effect evaporation chamber EV2 for further evaporation and concentration. In the II-effect evaporation chamber EV2, the III-effect evaporation chamber EV3, the IV-effect evaporation chamber EV4 and the V-effect evaporation chamber EV5, the same evaporation process as EV1 is repeated, and finally the brine reaches the concentration 26.10 wt% required by electrolysis. In the evaporation chamber from the II effect to the V effect, the operation temperature is respectively 103 ℃, 91 ℃, 74.8 ℃ and 59 ℃; the concentration of the brine flowing out of each effect evaporation chamber is 20.73 wt%, 21.69 wt%, 23.40 wt% and 26.10 wt% respectively.
The evaporation chambers from the first effect to the fourth effect are all falling film evaporators. The evaporation takes place on the surface of a thin falling film of brine inside the heat exchange tubes of the falling film evaporator. The hot brine enters the system at the upper part of the recirculation pipe or directly at the upper part of the evaporation chamber, and is uniformly distributed to each heat exchange pipe through a distributor in the barrel of the evaporation chamber, so that a layer of film is formed on the inner surface of each heat exchange pipe. The heat exchange tubes are heated by steam from the evaporator shell side, and the dilute brine then begins to evaporate. The brine film in the heat exchange tubes falls down on the one hand due to gravity and is pushed down on the other hand due to the steam produced. Two-phase flow is formed inside the heat exchange tube: steam and a thin brine film. Along the length direction of the heat exchange tube, the film is thinner and thinner, and the steam quantity is higher and higher. At the lower end of the heat exchange tube, steam and brine respectively leave the heating chamber, the steam directly enters the local effect steam chamber, and the brine directly enters the brine chamber of the local effect evaporation chamber. In each effect evaporation chamber, steam outlet pipeline and salt solution outlet pipeline all are located the lower extreme of evaporation chamber heat exchange tube, and steam outlet pipeline is slightly higher than salt solution outlet pipeline's position.
In effect II through effect V evaporation subsystems, the evaporation of the weak brine is produced not only by steam heating, but also by flashing of the hot brine, i.e., the hot brine enters a vessel with a lower operating pressure.
(4) After evaporation in the V-effect evaporation chamber EV5, the concentrated salt water product is sent to the battery limits through the product pump P06 at the speed of 87.56 t/h. The brine flow rate is controlled by a frequency converter of the product pump P06, which obtains a monitoring value from a density meter built into the fifth recirculation line RP 5. To minimize the amount of reject brine during start-up or load changes, an additional control valve CV is provided in the same line, which is slowly closed if a reject event occurs in the brine, such as too low a density, and the brine is returned to V-effect evaporator EV 5. When the density of the strong brine is close to the normal set value of 1193kg/m3The control valve CV is slowly opened and the brine is sent to the battery limits.
After evaporation in the V-effect evaporation chamber EV5, the concentration set point of the product strong brine is close to the brine saturation line. If the saturation line is exceeded, salt crystallization will begin to occur and the heater passes of the respective heating chambers will begin to foul. This phenomenon affects the evaporation efficiency, mainly the evaporation capacity of the device. Due to fluctuations in the control loop and variations in the feed composition, the crystallization risk is concentrated in the V-effect heating chamber HE 5. In order to avoid the influence of crystallization on the evaporation capacity or efficiency of the device in the operation process of the system, the V-effect evaporation chamber EV5 is set as a forced circulation evaporator and is monitored by a density measuring instrument in the recirculation pipeline RP5, so that the crystallization risk is reduced, and the production safety and the utilization efficiency are ensured. Meanwhile, a plurality of manual analysis sampling points and concentration analysis instruments are arranged for comparison analysis.
(5) Raw steam from a boundary area has the flow rate of 6.85t/h, the temperature of 290 ℃ and the pressure of 1200kPag, firstly enters the raw steam condensing tank CT1 through a distribution pipe below the raw steam condensing tank CT1 for temperature reduction, is directly contacted with condensed water (the flow rate of 7.32t/h and the temperature of 125 ℃) from an I-effect heating chamber HE1, the raw steam is accurately and automatically reduced in temperature according to the actual operation condition of the I-effect heating chamber HE1, the obtained saturated steam (the flow rate of 7.32t/h, the temperature of 126 ℃ and the pressure of 136kPag) enters the shell pass of the I-effect heating chamber HE1, and becomes condensate (the flow rate of 7.32t/h) after latent heat is released. The condensate leaves the bottom of the I-effect heating chamber HE1 and flows by gravity into raw steam condensate tank CT 1. The upper part of the raw steam condensing tank CT1 is connected with the shell side of an I-effect heating chamber HE1, and the pressure between the two containers is balanced. The condensate is continuously discharged from a raw steam condensing tank CT1 through a condensate pump P07 (the flow rate is 6.48t/h, the temperature is 126 ℃), reaches a first preheater PH1, and after the dilute brine is preheated, the condensate is cooled to 80 ℃ and leaves the unit and is sent to a battery limit. Since the condensate in the raw steam condensate tank CT1 is not polluted, the raw steam condensate can be directly sent back to the boiler room.
Steam from the I-effect evaporation chamber EV1, a small part (flow rate of 2.06t/h, temperature of 114 ℃ and pressure of 34kPag) is used as heating steam of the III preheater PH3, the rest (flow rate of 3.32t/h, temperature of 114 ℃ and pressure of 34kPag) is used as heating steam and enters the II-effect heating chamber HE2 for condensation, and condensate (flow rate of 5.38t/h, temperature of 108 ℃) reaches the shell side of the III-effect heating chamber HE3 through gravity flow. The operation of the II-effect evaporation chamber EV2 is similar to that of the I-effect evaporation chamber EV 1: the II-effect heating chamber HE2 is heated by steam from the I-effect evaporation chamber EV1, a small part of the generated steam (the flow rate is 2.54t/h, the temperature is 103 ℃, and the pressure is-11 kPag) flows to the II-effect preheater PH2, the rest part of the generated steam (the flow rate is 2.69t/h, the temperature is 103 ℃, and the pressure is-11 kPag) is used as heating steam to be condensed to the downstream III-effect heating chamber HE3, and the condensate reaches the shell side of the IV-effect heating chamber HE4 through gravity flow. Falling film evaporators are very sensitive to fouling and salt crystallization and use of a minimum flow rate prevents idling or crystallization of the tubes, i.e. prevents no liquid flowing through or crystallization in the tubes.
In the subsequent effect-III evaporation chamber EV3 and the effect-IV evaporation chamber EV4, all the generated steam is used for heating the next effect heating chamber.
Condensate (flow rate 4.81t/h, temperature 84.4 ℃) from the IV-effect heating chamber HE4 flows into a condensate tank CT2, and the condensate tank CT2 is connected with the shell side pressure of the V-effect heating chamber HE 5. The condensate tank CT2 collects all the condensate from the II-effect heating chamber HE2, the III-effect heating chamber HE3, the IV-effect heating chamber HE4 and the V-effect heating chamber HE 5. All the condensate (flow rate 15.21t/h, temperature 84.4 ℃) from the II-effect heating chamber HE2, the III-effect heating chamber HE3, the IV-effect heating chamber HE4 and the V-effect heating chamber HE5 is collected in a condensation tank CT 2. These condensates are sent to the battery limits by means of a first condensate pump P07. Due to the pressure difference, a part of the condensate is flashed in condensate tank CT2 into steam, which is reused as heating steam for the V-effect heating chamber HE5 (flow rate 0.14t/h, temperature 68.5 ℃, pressure-71 kPag).
The evaporation capacity of the system is controlled by the raw steam entering the evaporation device. Increasing the steam FIC loop settings, more steam enters the I-effect heating chamber HE1, which will result in more weak brine steam evaporating in the I-effect evaporation chamber EV1 and downstream evaporators. At the same time, the feed of the I-effect evaporator EV1 was increased with a corresponding increase in the weak brine due to the evaporator level control. As the steam flow into the system increases, the operating pressure of the evaporator will also increase accordingly. Therefore, the operating value of the steam FIC circuit can be indirectly increased by controlling the flow rate of the dilute brine and increasing the set value of the dilute brine FIC circuit.
[ example 2 ]
The system adopted in the embodiment is a triple-effect evaporation and concentration system, and compared with the embodiment 1, the equipment is different only in that: the first-effect evaporation chamber and the second-effect evaporation chamber are both falling-film evaporators, and the third-effect evaporation chamber is a forced circulation rising-film evaporator.
The technological process of evaporating, concentrating and recycling the triple-effect light salt water comprises the following specific steps:
(1) the flow rate of the fresh brine from the electrolysis system is 110.5t/h, the temperature is 75 ℃, the concentration is 18.80 wt%, and the fresh brine is preheated by a first preheater PH1, a second preheater PH2 and a third preheater PH3 in sequence, then is fed in parallel with steam and is sent to the tube side of an I-effect heating chamber HE 1. Wherein the outlet temperatures of the first preheater PH1, the second preheater PH2 and the third preheater PH3 are 88.2 ℃, 102.3 ℃ and 110 ℃, respectively.
(2) Saturated steam from a raw steam condensing tank CT1 enters an I-effect heating chamber EV1, and the flow rate of the saturated steam is 20.75t/h, the temperature is 126 ℃, and the pressure is 136kPag, and the weak saline water in an I-effect evaporation chamber EV1 is heated. Steam (flow rate of 10.94t/h, temperature of 114 ℃ and pressure of 34kPag) generated by the heated weak brine is used as a heating source of the II-effect evaporation chamber EV2 to enter the II-effect heating chamber HE2, steam (flow rate of 8.06t/h, temperature of 91 ℃ and pressure of-47 kPag) generated by the II-effect evaporation chamber EV2 enters the III-effect heating chamber HE3, steam (flow rate of 11.96t/h, temperature of 59 ℃ and pressure of-86 kPag) generated by the III-effect evaporation chamber EV3 enters a vacuum system, and condensed inert gas and/or non-condensable gas are removed through the vacuum system.
(3) The weak brine preheated by the first preheater pH1, the second preheater pH2 and the third preheater pH3 was 110 ℃ and was close to the operating temperature of the first effect evaporator EV1 of 114 ℃. The light salt water heated by the I-effect heating chamber HE1 is evaporated in the I-effect evaporation chamber, and the salt concentration is increased to 20.86 wt%. The pre-concentrated weak brine leaves the I-effect evaporation chamber EV1 through an I-effect pump P01 and flows to the II-effect evaporation chamber EV2 for further evaporation and concentration. Effect II and effect III evaporation the same evaporation process as EV1 was repeated and the final brine reached the required concentration of 26.10 wt% for electrolysis. In the evaporation chambers of the effect II and the effect III, the operation temperatures are 91 ℃ and 59 ℃ respectively; the concentration of the brine flowing out of each effect evaporation chamber is 22.68 wt% and 26.10 wt% respectively.
(4) Raw steam from the battery limits at a flow rate of 18.92t/h, a temperature of 290 ℃ and a pressure of 1200kPag enters a raw steam condensation tank CT1 to be cooled. Raw steam enters through a distribution pipe below a raw steam condensation tank and is in direct contact with condensed water (flow rate 20.62t/h, temperature 125 ℃) from the I-effect heating chamber HE1, and the raw steam is automatically and accurately cooled according to the actual operation condition of the I-effect heating chamber HE 1. The resulting saturated steam (flow rate 20.62t/h, temperature 126 ℃, pressure 136kPag) enters an I-effect heating chamber HE 1. The steam heating the I-effect heating chamber HE1 becomes condensate after releasing latent heat on the shell side (flow rate 20.62 t/h). The condensate leaves the bottom of the I-effect heating chamber HE1 and flows by gravity into raw steam condensate tank CT 1. The upper part of the raw steam condensing tank CT1 is connected with the shell side of an I-effect heating chamber HE1, and the pressure between the two containers is balanced. The condensate is continuously discharged from the condensate tank through a condensate pump P07 (the flow rate is 18.35t/h, the temperature is 126 ℃) and reaches a first preheater PH1, after the dilute brine is preheated, the condensate is cooled to 80 ℃ and leaves the unit, and is sent to a battery limit and returned to a boiler room.
Steam from the I-effect evaporation chamber EV1, a part (flow rate 3.16t/h, temperature 114 ℃ C., pressure 34kPag) is used as heating steam for the III-preheater PH3, and the rest (flow rate 7.78t/h, temperature 114 ℃ C., pressure 34kPag) is used as heating steam to enter the II-effect heating chamber HE2, condensed in the heating chamber HE, and condensate (flow rate 10.94t/h, temperature 108 ℃ C.) is discharged from the system through gravity flow to reach the shell side of the III-effect heating chamber HE 3. The operation of the II-effect evaporation chamber EV2 is similar to EV 1: steam is generated in the II-effect evaporation chamber EV2, one part (the flow rate is 3.82t/h, the temperature is 91 ℃ and the pressure is-47 kPag) flows to the II preheater PH2, and the other part (the flow rate is 4.24t/h, the temperature is 91 ℃ and the pressure is-47 kPag) serves as heating steam to flow to the downstream III-effect heating chamber HE 3.
Condensate (flow rate 7.55t/h, temperature 84.4 ℃) from the II-effect heating chamber HE2 flows into a condensate tank CT2, and the condensate tank CT2 is connected with the shell side pressure of the III-effect heating chamber HE 3. The condensate tank CT2 also collects condensate from the III-effect heating chamber HE 3. All the condensate (flow rate 30.86t/h, temperature 84.7 ℃) from the II-effect heating chamber HE2 and the III-effect heating chamber HE3 is collected in a condensation tank CT 2. These condensates are sent to the battery limits by means of a first condensate pump P07. Due to the pressure difference, a part of the condensate flashes into steam which is reused as heating steam for the III-effect heating chamber HE3 (flow rate 1.22t/h, temperature 68.5 ℃, pressure-71 kPag).
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, but rather extends to all other methods and applications having the same functionality.
Claims (10)
1. A brine evaporation and concentration system comprises a preheating subsystem, an evaporation subsystem and a steam subsystem; the evaporation subsystem comprises a condensate tank, an I-effect evaporation subsystem, a II-effect evaporation subsystem and an N-effect evaporation subsystem, wherein the I-effect evaporation subsystem and the II-effect evaporation subsystem are sequentially connected in series, and each of the I-effect evaporation subsystem and the II-effect evaporation subsystem respectively and independently comprises an evaporation chamber, a heating chamber, a pump and a corresponding pipeline in corresponding levels; the I-effect to N-1-effect evaporation chambers are all falling-film evaporators, and the N-effect evaporation chamber is a forced circulation rising-film evaporator;
in the evaporation subsystems from the effect I to the effect N-1, a bottom discharge hole of the evaporation chamber is connected with a top feed hole of the heating chamber through a pump, and a bottom discharge hole of the heating chamber is connected with a lower feed hole of the evaporation chamber; one branch of the discharge hole of the pump with the first effect is connected with the top feed inlet of the heating chamber with the second effect; a discharge port at the top of the front-effect evaporation chamber is connected with a shell pass feed inlet of the rear-effect heating chamber;
in the Nth-effect evaporation subsystem, a discharge port at the top of the evaporation chamber is connected with a vacuum system; a discharge port at the lower part of the evaporation chamber is connected with a feed port at the bottom of the heating chamber through a pump, and a discharge port at the top of the heating chamber is connected with a feed port of the evaporation chamber; a product extraction outlet is arranged on a connecting pipeline of the lower discharging part of the evaporation chamber and the bottom feeding hole of the heating chamber, the product extraction outlet is connected with a product extraction pipeline, and a product pump is preferably arranged on the product extraction pipeline; a branch of a discharge hole of the N-1 th-effect pump is connected with a feed hole of the N-1 th-effect pump, and a discharge hole at the top of the N-1 th-effect evaporation chamber is connected with a shell pass feed hole of the N-1 th-effect heating chamber;
in the evaporation subsystems of the second effect to the N effect, a shell pass discharge port of each effect heating chamber is connected with a condensate tank, and preferably, an outlet of the condensate tank is connected with a second condensate pump; optionally, a shell pass discharge port of the first-effect heating chamber is connected with a condensate tank;
optionally, the shell side of each effect heating chamber further comprises a non-condensable gas outlet, and the non-condensable gas outlets of the effect heating chambers are connected with the vacuum system respectively and independently;
the preheating subsystem comprises a plurality of preheaters which are sequentially connected in series, and a discharge hole of the preheating subsystem is connected with a top feed inlet of the I-effect heating chamber;
a raw steam outlet of the steam subsystem is connected with a shell pass feed inlet of the I-effect heating chamber; preferably, the steam subsystem further comprises a raw steam condensate tank, a raw steam outlet is connected with a raw steam distribution pipe in the raw steam condensate tank, a gas-phase outlet of the raw steam condensate tank is connected with a shell pass feed inlet of the I-effect heating chamber, and a liquid-phase outlet of the raw steam condensate tank is connected with an inlet of any preheater in the preheating subsystem;
n is a positive integer of 2 or more, preferably N is a positive integer of 3 to 8, and more preferably N-5.
2. The system of claim 1, wherein in the N-th effect evaporation subsystem, a density measuring instrument is arranged in a pipeline connecting a discharge port at the top of the heating chamber with a feed port of the evaporation chamber, and a branch of an outlet of the product pump is connected with an inlet of the N-th effect pump through an unqualified concentrated brine return pipeline; and the control valve matched with the built-in density measuring instrument is arranged on a strong brine product extraction pipeline.
3. The system according to claim 1 or 2, wherein the raw steam distribution pipe is installed inside the condensation tank in an inner insertion pipe type, and the pipe wall is provided with distribution holes, preferably, the hole diameter of the distribution holes is phi 5-phi 50, more preferably, phi 20-phi 50.
4. The system of any one of claims 1-3, wherein each effective heating chamber is independently a shell and tube heat exchanger comprising a barrel, a heat exchange tube bundle, and a demister device located at the top within the barrel;
preferably, the demisting device further comprises a matched cleaning nozzle, and the spray range of the cleaning nozzle has a cone angle of 50-150 degrees, more preferably 90-120 degrees;
preferably, a distributor or a distribution disc is arranged at the top of the heat exchange tube bundle of each effect heating chamber, and the distributor or the distribution disc is preferably in a grid or sieve plate type; more preferably, the size of the sieve pore of the distributor or the distribution plate is phi 5-phi 50;
preferably, the inner tube bundle of the heating chamber is a single-pass tube bundle, and the length-diameter ratio of the tube bundle is 50-500, preferably 100-400, and more preferably 200-300.
5. The system of any one of claims 1-4, wherein one branch of the top discharge of each effect evaporation chamber is independently connected to the steam feed of any preheater in the evaporation subsystem;
preferably, the condensate tank is connected with the shell side pressure of the Nth effective heater;
preferably, a discharge hole at the top of the condensate tank is connected with a shell pass feed inlet of the Nth efficient heating chamber;
preferably, in the front N-1-effect evaporation subsystem, a pipeline connecting the front-effect pump and the top feed inlets of the rear-effect heating chamber is connected with a liquid level control device.
6. A brine evaporative concentration process comprising:
(1) the light salt water enters the I-effect evaporation subsystem and the II-effect evaporation subsystem in sequence after being preheated until the N-effect evaporation subsystem is concentrated; in each effect evaporation subsystem, the preheated dilute brine enters an I-effect evaporation chamber for evaporation after being heated by a tube pass of the I-effect heating chamber; the pre-concentrated light salt water leaves the I-effect evaporation chamber through the I-effect pump, flows to the II-effect evaporation chamber and is further evaporated and concentrated; repeating the same evaporation process as the I-effect evaporation chamber in the II-effect evaporation chamber, the III-effect evaporation chamber and the N-effect evaporation chamber until the salt water reaches the required concentration;
preferably, the weak brine is fed concurrently with the heating medium of the pre-heating subsystem;
(2) raw steam from a battery compartment enters a shell pass of the I-effect heating chamber to heat the dilute brine, and the temperature of the dilute brine preheated by the preheating subsystem is close to the operating temperature of the I-effect evaporation chamber;
preferably, the raw steam firstly enters the raw steam condensing tank through a distribution pipe below the raw steam condensing tank, and is contacted with condensed water from a shell pass discharge port of the I-effect heating chamber, and the obtained saturated steam enters a shell pass feed port of the I-effect heating chamber;
(3) the method comprises the following steps that (1) the I-effect evaporation chamber is communicated with the N-effect evaporation chamber, steam obtained by evaporating the light salt water in the previous effect evaporation chamber is used as a heat source of the next effect heating chamber and enters the shell pass of the next effect heating chamber, and steam in the Nth effect evaporation chamber is discharged out of a salt water evaporation and concentration system;
preferably, the steam for heating the I-effect heating chamber becomes condensate after latent heat is released on the shell side, and the condensate leaves the bottom of the I-effect heating chamber and flows into a raw steam condensate tank; more preferably, the condensate is continuously discharged from the raw steam condensate tank through a first condensate pump, reaches an I preheater of the preheating subsystem, and is sent to a battery compartment after the dilute brine is preheated;
(4) the strong brine product is sent to a battery compartment after being evaporated by the N-effect evaporation chamber;
preferably, the product concentration is controlled by a density measuring instrument and a control valve which are arranged in a recirculation pipe connecting the N-effect evaporation chamber and the N-effect heating chamber, when the strong brine is unqualified, the control valve is closed, and the strong brine returns to the N-effect evaporation subsystem; when the strong brine is qualified, opening the control valve and sending the strong brine to a boundary area;
(5) the condensate tank collects all the condensate from the II-effect heating chamber to the N-effect heating chamber and optional condensate of the I-effect heating chamber, and the condensate is pumped to the battery compartment through the second condensate;
preferably, part of the condensate in the condensate tank is flashed into steam in the condensate tank and enters the N-effect heating chamber.
7. The process of claim 6, wherein the steam generated from the effect evaporation chamber is partially used as heating steam of the effect heating chamber III, and the rest part is used as heating steam to enter the effect heating chamber II, preferably the condensate in the effect heating chamber II enters the shell side of the effect heating chamber III through gravity flow; more preferably, the flow ratio of the heating steam used as the third preheater to the heating steam used as the II-effect heating chamber is (0.2-3): 1, and more preferably (0.5-1): 1.
8. The process of claim 6 or 7, wherein part of the steam generated from the evaporation chamber of effect II is used as heating steam for the preheater of effect II, and the rest is used as heating steam to enter the heating chamber of effect III, preferably the condensate in the heating chamber of effect III enters the shell side of the heating chamber of effect IV through gravity flow; more preferably, the flow ratio of the heating steam used as the second preheater to the heating steam used as the third-effect heating chamber is (0.2-3): 1, and more preferably (0.5-1): 1.
9. Use of the brine evaporative concentration system of any one of claims 1 to 5 or the brine evaporative concentration process of any one of claims 6 to 8 in the field of brine concentration treatment.
10. Use of the brine evaporative concentration system of any one of claims 1 to 5 or the brine evaporative concentration process of any one of claims 6 to 8 in the concentration treatment of electrolytically dechlorinated brackish water at a concentration of from 100g/L to 220 g/L; preferably, the brine evaporative concentration system includes a five-effect evaporation subsystem.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105217703A (en) * | 2015-11-05 | 2016-01-06 | 陕西省石油化工研究设计院 | A kind of sextuple-effect evaporation crystallization apparatus and technique thereof being applied to zero discharge of industrial waste water |
| CN111994980A (en) * | 2020-08-20 | 2020-11-27 | 广东闻扬环境科技有限公司 | Sewage treatment system |
| CN215136949U (en) * | 2020-12-22 | 2021-12-14 | 中国天辰工程有限公司 | Multi-effect brine evaporation and concentration system for ionic membrane electrolysis |
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2020
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105217703A (en) * | 2015-11-05 | 2016-01-06 | 陕西省石油化工研究设计院 | A kind of sextuple-effect evaporation crystallization apparatus and technique thereof being applied to zero discharge of industrial waste water |
| CN111994980A (en) * | 2020-08-20 | 2020-11-27 | 广东闻扬环境科技有限公司 | Sewage treatment system |
| CN215136949U (en) * | 2020-12-22 | 2021-12-14 | 中国天辰工程有限公司 | Multi-effect brine evaporation and concentration system for ionic membrane electrolysis |
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