CN115006857B - Intermittent evaporation crystallization device and process adopting two-effect parallel evaporation - Google Patents
Intermittent evaporation crystallization device and process adopting two-effect parallel evaporation Download PDFInfo
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- CN115006857B CN115006857B CN202210771578.1A CN202210771578A CN115006857B CN 115006857 B CN115006857 B CN 115006857B CN 202210771578 A CN202210771578 A CN 202210771578A CN 115006857 B CN115006857 B CN 115006857B
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- 238000002425 crystallisation Methods 0.000 title claims abstract description 233
- 230000008025 crystallization Effects 0.000 title claims abstract description 233
- 238000001704 evaporation Methods 0.000 title claims abstract description 51
- 230000008020 evaporation Effects 0.000 title claims abstract description 45
- 238000000034 method Methods 0.000 title claims description 31
- 230000008569 process Effects 0.000 title claims description 27
- 238000011084 recovery Methods 0.000 claims abstract description 19
- 238000007599 discharging Methods 0.000 claims abstract description 12
- 238000004094 preconcentration Methods 0.000 claims description 50
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 45
- 239000007788 liquid Substances 0.000 claims description 43
- 238000003756 stirring Methods 0.000 claims description 25
- 238000002156 mixing Methods 0.000 claims description 9
- 238000004064 recycling Methods 0.000 claims description 9
- 230000007246 mechanism Effects 0.000 claims description 8
- 238000000926 separation method Methods 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 3
- NWONKYPBYAMBJT-UHFFFAOYSA-L zinc sulfate Chemical compound [Zn+2].[O-]S([O-])(=O)=O NWONKYPBYAMBJT-UHFFFAOYSA-L 0.000 description 13
- 229960001763 zinc sulfate Drugs 0.000 description 13
- 229910000368 zinc sulfate Inorganic materials 0.000 description 13
- 230000000694 effects Effects 0.000 description 10
- 239000013078 crystal Substances 0.000 description 8
- 230000002411 adverse Effects 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 239000012452 mother liquor Substances 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000018044 dehydration Effects 0.000 description 2
- 238000006297 dehydration reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229940118149 zinc sulfate monohydrate Drugs 0.000 description 2
- RNZCSKGULNFAMC-UHFFFAOYSA-L zinc;hydrogen sulfate;hydroxide Chemical compound O.[Zn+2].[O-]S([O-])(=O)=O RNZCSKGULNFAMC-UHFFFAOYSA-L 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 239000005394 sealing glass Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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
- B01D9/00—Crystallisation
- B01D9/02—Crystallisation from solutions
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G9/00—Compounds of zinc
- C01G9/06—Sulfates
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B37/00—Component parts or details of steam boilers
- F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
- F22B37/26—Steam-separating arrangements
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22D—PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS
- F22D11/00—Feed-water supply not provided for in other main groups
- F22D11/02—Arrangements of feed-water pumps
- F22D11/06—Arrangements of feed-water pumps for returning condensate to boiler
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Water Supply & Treatment (AREA)
- Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
Abstract
The invention relates to an intermittent evaporation crystallization device adopting two-effect parallel evaporation, which is characterized by comprising a one-effect crystallization tank internally provided with a one-effect steam coil, a two-effect crystallization tank internally provided with a two-effect steam coil, a raw steam recovery part and a centrifugal crystallization part, wherein the one-effect crystallization tank and the two-effect crystallization tank are both sealed tank bodies, a raw steam conveying pipe for introducing raw steam generated by an external boiler is arranged on the one-effect crystallization tank, and an air inlet of the one-effect steam coil is communicated with the external raw steam conveying pipe; the primary mixed steam pipe communicated with the steam coil pipe in the secondary crystallization tank is also arranged on the primary crystallization tank; the air outlet pipe of the raw steam recovery part is communicated with the primary mixed steam pipe, and the air inlet pipe is communicated with the outlet of the primary steam coil; and the feeding end of the centrifugal crystallization part is respectively communicated with the discharging ends of the first-effect crystallization tank and the second-effect crystallization tank through a discharge bottom valve.
Description
Technical Field
The invention belongs to the technical field of chemical crystallization devices and processes, and particularly relates to a device and a process for intermittent evaporation crystallization by adopting two-effect parallel evaporation.
Background
The zinc sulfate monohydrate product is mainly obtained by heating, concentrating and crystallizing zinc sulfate solution, the existing zinc sulfate concentrating and crystallizing is mainly obtained by using an open crystallization kettle, the zinc sulfate solution is heated by steam to boil, water in the solution is discharged from the crystallization kettle in a steam mode, so that the zinc sulfate solution is continuously concentrated and crystallized, and when the zinc sulfate solution is concentrated to meet the dehydration condition, the zinc sulfate can be centrifugally dehydrated, so that the zinc sulfate monohydrate product is obtained.
However, in the process of crystallizing zinc sulfate in an open crystallization kettle, secondary steam generated by the heated solution and used raw steam can be directly discharged into the air and cannot be recycled, the consumption of the raw steam is large, the crystallization energy consumption is high, and meanwhile, the steam discharge is easy to cause workshop scalding accidents and can cause certain adverse effects on the surrounding environment;
in addition, because the open crystallization kettle is used for concentrating and crystallizing under normal pressure, the speed of concentrating and crystallizing is low, the time is long, and the efficiency of concentrating and crystallizing in unit time is low; meanwhile, when zinc sulfate meeting the dehydration condition in the open crystallization kettle is discharged, the concentration crystallization is in a stop state, and the concentration crystallization cannot be continuously carried out, so that the crystallization time of the zinc sulfate is further prolonged, and the concentration crystallization efficiency of the open crystallization kettle in unit time is low.
Disclosure of Invention
The invention aims to provide a device and a process for intermittent evaporative crystallization by adopting two-effect parallel evaporation, which are used for solving the technical problems that the energy consumption of the evaporative crystallization is high, the service time is long, the efficiency is low, steam scalding accidents are easy to occur, and the surrounding environment is influenced by high temperature in the prior art.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the intermittent evaporation crystallization device comprises a first-effect crystallization tank, a second-effect crystallization tank, a raw steam recovery part and a centrifugal crystallization part, wherein the first-effect crystallization tank is internally provided with a first-effect steam coil, the second-effect crystallization tank is internally provided with a second-effect steam coil, the first-effect crystallization tank and the second-effect crystallization tank are sealed tank bodies, a raw steam conveying pipe for introducing raw steam generated by an external boiler is arranged on the first-effect crystallization tank, and an air inlet of the first-effect steam coil is communicated with the external raw steam conveying pipe;
the primary mixed steam pipe communicated with the steam coil pipe in the secondary crystallization tank is also arranged on the primary crystallization tank; the air outlet pipe of the raw steam recovery part is communicated with the primary mixed steam pipe, and the air inlet pipe is communicated with the outlet of the primary steam coil;
and the feeding end of the centrifugal crystallization part is respectively communicated with the discharging ends of the first-effect crystallization tank and the second-effect crystallization tank through a discharge bottom valve.
The device also comprises a pre-concentration tank with a steam coil and a mixed steam recovery part, wherein a secondary mixed steam pipe communicated with the air inlet end of the steam coil in the pre-concentration tank is arranged on the secondary crystallization tank;
the air inlet pipe of the mixed steam recovery part is respectively communicated with the steam coil pipe in the secondary crystallization tank and the steam coil pipe in the pre-concentration tank, and the air outlet pipe is communicated with the secondary mixed steam pipe.
The feed end of the pre-concentration tank is communicated with external finished water through a finished water feed pipe, and the discharge end of the pre-concentration tank is communicated with the feed inlets of the first-effect crystallization tank and the second-effect crystallization tank through a pump body, a liquid conveying pipeline and a valve body arranged on the liquid conveying pipeline respectively.
Stirring mechanisms are arranged in the first-effect crystallization tank, the second-effect crystallization tank and the pre-concentration tank.
The raw steam recovery part comprises a raw steam gas-liquid separator, the mixed steam recovery part comprises a mixed steam gas-liquid separator, and condensate liquid outlet ends of the raw steam gas-liquid separator and the mixed steam gas-liquid separator are respectively communicated with an external steam boiler through steam condensate water pipes.
A two-effect parallel evaporation intermittent evaporation crystallization process comprises the following steps,
A. injecting a solution to be crystallized into the first-effect crystallization tank and the second-effect crystallization tank respectively, conveying raw steam into the first-effect crystallization tank, stirring the solution in the first-effect crystallization tank, and evaporating and crystallizing the solution;
B. recovering the raw steam output from the first-effect crystallization tank, mixing the recovered raw steam with secondary steam generated in the evaporation and crystallization process of the first-effect crystallization tank to form primary mixed steam, conveying the primary mixed steam into the second-effect crystallization tank, stirring the solution in the second-effect crystallization tank, and performing evaporation and crystallization on the solution by using the primary mixed steam;
C. discharging the solution in the first-effect crystallization tank to a centrifugal crystallization part after the concentration of the solution in the first-effect crystallization tank reaches 60-85 Baume degrees, and centrifuging to obtain a product;
D. and discharging the solution in the two-effect crystallization tank to a centrifugal crystallization part after the concentration of the solution in the two-effect crystallization tank reaches 60 to 85 Baume degrees, and centrifuging to obtain a product.
It also comprises the steps of,
E. continuously injecting the finished product water into a pre-concentration tank, recovering primary mixed steam output from a secondary crystallization tank, mixing the recovered primary mixed steam with secondary steam generated in the evaporation and crystallization process of the secondary crystallization tank to form secondary mixed steam, conveying the secondary mixed steam into the pre-concentration tank, stirring the finished product water in the pre-concentration tank, and continuously pre-concentrating the finished product water in the pre-concentration tank by utilizing the secondary mixed steam;
F. after the concentration of the product water reaches 30 to 55 Baume degrees, the product water is injected into a first-effect crystallization tank or a second-effect crystallization tank for evaporation and crystallization;
G. and E, recycling the secondary mixed steam output from the pre-concentration tank, and mixing the recycled secondary mixed steam with the secondary mixed steam in the step E again and conveying the mixture to the pre-concentration tank.
The raw steam, the primary mixed steam and the secondary mixed steam are recovered after gas-liquid separation.
The beneficial effects of adopting above-mentioned technical scheme to produce lie in:
according to the device and the process for crystallizing by adopting the two-effect parallel evaporation and intermittent evaporation, the secondary steam generated in the process of recycling the primary steam and crystallizing is mixed into the primary mixed steam and the secondary mixed steam, and the primary mixed steam and the secondary mixed steam are put into the next crystallizing tank or the pre-concentrating tank, so that the heat energy of the primary steam is fully utilized, the heat energy utilization rate of the primary steam is improved, the use amount of the primary steam is obviously reduced in the process of evaporating and crystallizing the same amount of solution, and the crystallizing energy consumption is reduced;
secondly, the sealed tank body is adopted for crystallization, the air pressure in the tank body is controlled to be evaporated and crystallized in a specified pressure interval, a high-pressure environment is created for the solution in the first-effect crystallization tank and the second-effect crystallization tank, the solution evaporation and crystallization can be effectively accelerated, the evaporation and crystallization time of the solution under unit capacity is obviously shortened, moreover, the steam scalding accident can be effectively avoided due to the fact that the steam is prevented from being discharged outwards, and adverse effects of the discharged steam on the surrounding environment are avoided;
in addition, in the process of recycling raw steam, primary mixed steam and secondary mixed steam, the raw steam, the primary mixed steam and the secondary mixed steam are subjected to gas-liquid separation, pure steam condensate water can be obtained through separation, and the pure steam condensate water is led into a boiler for generating the raw steam, so that the recycling of the raw steam and water in a solution can be realized, and the water source consumption is reduced.
According to the technical scheme provided by the invention, through recycling the steam, the energy contained in the raw steam and the secondary steam generated in the crystallization process is fully utilized, the heat energy utilization rate is high, the crystallization energy consumption is obviously reduced, the crystallization time is effectively shortened, the crystallization efficiency and yield are improved, the production benefit of enterprises is improved, and the adverse effect of the discharged hot steam on the environment can be effectively reduced due to the reduction of the externally discharged steam, so that the method is beneficial to popularization and use in the chemical crystallization field.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
fig. 2 is a process flow diagram of the present invention.
The figure indicates: 1. the device comprises a first-effect crystallization tank, 2, a second-effect crystallization tank, 301, a first-effect steam coil, 302, a second-effect steam coil, 303, a pre-concentration steam coil, 4, a raw steam conveying pipe, 5, a primary mixed steam pipe, 6, a centrifugal machine, 7, a pre-concentration tank, 8, a secondary mixed steam pipe, 9, a finished water feeding pipe, 10, a stirring mechanism, 11, a stirring motor, 12, a stirring paddle, 13, a raw steam gas-liquid separator, 14, a mixed steam gas-liquid separator, 15, a viewing hole, 16, a discharge bottom valve, 17 and a steam condensate pipe.
Detailed Description
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which the objects, structures, and functions of the invention are shown.
This example is exemplified by the evaporative crystallization of zinc sulfate, which is specifically as follows:
as shown in fig. 1, the invention provides a batch evaporation crystallization device adopting two-effect parallel evaporation, which comprises a one-effect crystallization tank 1 provided with a one-effect steam coil 301, a two-effect crystallization tank 2 provided with a two-effect steam coil 302, a raw steam recovery part and a centrifugal crystallization part, wherein the one-effect crystallization tank 1 and the two-effect crystallization tank 2 are sealed tank bodies, so that the pressure in the one-effect crystallization tank 1 and the two-effect crystallization tank 2 is controlled within a specified range, and a proper pressure environment is provided for evaporation crystallization of solution, so that the speed of evaporation crystallization is accelerated, and the efficiency of evaporation crystallization is improved; the first-effect crystallization tank 1 is provided with a raw steam conveying pipe 4 for introducing raw steam generated by an external boiler, an air inlet of the first-effect steam coil 301 is communicated with the external raw steam conveying pipe 4, after the solution to be crystallized is injected into the first-effect crystallization tank 1, raw steam is introduced into the first-effect steam coil 301, and the solution is evaporated and crystallized under the action of heat contained in the raw steam.
In addition, the primary mixed steam pipe 5 communicated with the secondary steam coil 302 in the secondary crystallization tank 2 is also arranged on the primary crystallization tank 1, and secondary steam generated in the crystallization process of the solution in the primary crystallization tank 1 is led into the secondary steam coil 302 through the primary mixed steam pipe 5; meanwhile, in order to recover the raw steam and condensed water therein output from the first-effect crystallization tank 1, so as to make full use of heat in the raw steam, the raw steam recovery part in this embodiment includes a raw steam gas-liquid separator 13 and other accessories such as pipelines and valves matched with the raw steam gas-liquid separator 13, an air outlet pipe of the raw steam gas-liquid separator 13 is communicated with the primary mixed steam pipe 5 through a pipeline, an air inlet pipe is communicated with an outlet of the first-effect steam coil 301 through a pipeline, the recovered raw steam is subjected to gas-liquid separation by the raw steam gas-liquid separator 13 to obtain pure condensed water and raw steam, and the separated raw steam is introduced into the primary mixed steam pipe 5 to be mixed with secondary steam therein to form primary mixed steam for evaporating and crystallizing the solution in the second-effect crystallization tank 2.
Further, in order to facilitate the guiding out of the residual solution and crystals after the evaporation in the first-effect crystallization tank 1 and the second-effect crystallization tank 2 from the first-effect crystallization tank 1 and the second-effect crystallization tank 2, the feeding end of the centrifugal crystallization part is respectively communicated with the discharging ends of the first-effect crystallization tank 1 and the second-effect crystallization tank 2 through a discharge bottom valve 16, and the centrifugal crystallization part in the embodiment comprises a centrifuge 6 and other accessories matched with the centrifuge 6 to work.
Further, in order to recover the primary mixed steam output from the secondary crystallization tank 2 and make full use of heat in the primary mixed steam, the crystallization device further comprises a pre-concentration tank 7 with a pre-concentration steam coil 303 and a mixed steam recovery part, wherein the secondary mixed steam pipe 8 communicated with the air inlet end of the steam coil in the pre-concentration tank 7 is arranged on the secondary crystallization tank 2; the feed end of the pre-concentration tank 7 is communicated with external finished water through a finished water feed pipe 9, and the discharge end of the pre-concentration tank 7 is communicated with the feed inlets of the first-effect crystallization tank 1 and the second-effect crystallization tank 2 through a pump body, a liquid conveying pipeline and a valve body arranged on the liquid conveying pipeline respectively.
The mixed steam recovery part comprises a mixed steam gas-liquid separator 14 and other accessories such as pipelines, valves and the like matched with the mixed steam gas-liquid separator, wherein an air inlet pipe of the mixed steam gas-liquid separator 14 is respectively communicated with an air outlet of the secondary steam coil 302 and an air outlet of the pre-concentration steam coil 303, and an air outlet pipe is communicated with the secondary mixed steam pipe 8. The primary mixed steam output from the double-effect steam coil 302 is recovered and separated by the mixed steam gas-liquid separator 14 to obtain pure condensed water and primary mixed steam, and the separated primary mixed steam is introduced into the secondary mixed steam pipe 8 and mixed with the secondary steam therein to form secondary mixed steam for pre-concentrating the finished water in the pre-concentration tank 7.
In addition, in order to provide a high-pressure crystallization environment for the solution in the tank body, so as to increase the crystallization speed and shorten the crystallization time, in this embodiment, the first-effect crystallization tank 1 and the second-effect crystallization tank 2 are provided as sealed tank bodies, and the air pressure in the first-effect crystallization tank 1 and the second-effect crystallization tank 2 is controlled by providing pressure regulating valves at the air inlet of the first-effect mixed steam pipe 5 and the air inlet of the second-effect mixed steam pipe 8, the opening pressure of the pressure regulating valve on the first-effect mixed steam pipe 5 is set to be 0.35MPa, the opening pressure of the pressure regulating valve on the second-effect mixed steam pipe 8 is set to be 0.15MPa, and when the air pressures in the first-effect crystallization tank 1 and the second-effect crystallization tank 2 respectively exceed 0.35MPa and 0.15MPa, the pressure regulating valves are opened, and the secondary steam in the first-effect crystallization tank 1 is input into the first-effect mixed steam pipe 5, and the secondary steam in the second-effect crystallization tank 2 is input into the second-effect mixed steam pipe 8. The arrangement of the sealed type tank body of the first-effect crystallization tank 1 and the second-effect crystallization tank 2 can also avoid the occurrence of the consequences of scalding workers and causing adverse effects on the surrounding environment due to the outward discharge of secondary steam.
Further, in order to promote the evaporation and crystallization of the solution in the first-effect crystallization tank 1 and the second-effect crystallization tank 2 and promote the pre-concentration of the product water in the pre-concentration tank 7, the crystallization product is at the bottom, in this embodiment, stirring mechanisms 10 are respectively disposed in the first-effect crystallization tank 1, the second-effect crystallization tank 2 and the pre-concentration tank 7, each stirring mechanism 10 is respectively adapted to the corresponding tank (here, the tank is a generic name of the first-effect crystallization tank 1, the second-effect crystallization tank 2 and the pre-concentration tank 7), and comprises a stirring motor 11 disposed outside the tank and a stirring paddle 12 disposed inside the tank, wherein the stirring motor 11 is in transmission connection with the stirring paddle 12, and the stirring speed is about 60 revolutions per minute and is used for stirring the solution or the product water.
Further, in this embodiment, the condensate liquid ends of the vapor-generating gas-liquid separator 13 and the mixed vapor-gas-liquid separator 14 are respectively communicated with an external vapor boiler through a vapor condensate pipe 17, so as to guide pure condensate water obtained by the vapor-liquid separation back to the boiler, generate vapor again, and be used for evaporative crystallization, thereby fully utilizing water in the vapor and water in the solution, saving water sources, and reducing external water consumption.
Further, in order to facilitate observation of the liquid level in the crystallization tank and crystallization condition of the solution, in this embodiment, observation holes 15 are respectively provided at the tops of the first-effect crystallization tank 1 and the second-effect crystallization tank 2, and sealing glass is provided on the observation holes 15 for keeping the sealing type of the tank.
Above-mentioned setting has realized that the feeding of first effect crystallization jar 1 and second effect crystallization jar 2 is parallelly connected and raw steam is parallelly connected, and solution concentration in first effect crystallization jar 1 is to satisfying centrifugal condition and is discharged remaining solution and crystallization crystal to centrifuge 6's in-process through blowing bottom valve 16, and raw steam can be continued to evaporate crystallization through the second effect crystallization jar 2 of raw steam recovery unit introduction, can continue in the second effect crystallization jar 2 promptly, does not receive the influence of first effect crystallization jar 1, so, crystallization can go on in succession uninterrupted to, further shortened the crystallization time of device whole to unit volume solution, improved crystallization efficiency.
As shown in fig. 2, a process of intermittent evaporative crystallization by two-effect parallel evaporation comprises the following steps:
A. injecting the solution to be crystallized into the tank bodies of the first-effect crystallization tank 1 and the second-effect crystallization tank 2 respectively, when the solution is injected to the height of 3/4 of the tank body in the tank body, starting to convey raw steam into the first-effect crystallization tank 1, conducting heat to the solution in the first-effect crystallization tank 1 through the first-effect steam coil 301, stirring the solution in the first-effect crystallization tank 1 by the stirring mechanism 10, and evaporating and crystallizing the solution;
in order to make the raw steam complete the two-effect crystallization of the one-effect crystallization tank 1 and the two-effect crystallization tank 2 and not cause excessive heat waste, the temperature range of the raw steam input into the one-effect crystallization tank 1 should be controlled within 150 to 190 ℃, preferably, the temperature of the raw steam input into the one-effect crystallization tank 1 is selected to be about 170 ℃ and the pressure is about 0.6MPa in the embodiment;
B. the method comprises the steps of recycling raw steam and condensed water output from a first-effect steam coil 301 by a raw steam gas-liquid separator 13, performing gas-liquid separation on the raw steam, inputting the separated raw steam into a first-effect mixed steam pipe 5, mixing the raw steam with secondary steam generated in the evaporation and crystallization process of a first-effect crystallization tank 1 to form first mixed steam, conveying the first mixed steam into a second-effect crystallization tank 2 through the first-effect mixed steam pipe 5, performing evaporation and crystallization on a solution in the second-effect crystallization tank 2, and stirring the solution in the second-effect crystallization tank 2 by a stirring mechanism 10 for promoting the evaporation and crystallization;
C. after the concentration of the solution in the first-effect crystallization tank 1 reaches 60 to 85 Baume degrees, opening a discharging bottom valve 16, discharging the residual solution and the crystallized crystals into a centrifugal machine 6 of a centrifugal crystallization part, and starting and centrifuging the centrifugal machine 6 to obtain a zinc sulfate product; preferably, in this embodiment, when the crystallization concentration reaches 75 Baume degrees, the residual solution and crystals in the first-effect crystallization tank 1 are discharged to the centrifuge 6;
D. after the concentration of the solution in the two-effect crystallization tank 2 reaches 60 to 85 Baume degrees, opening a discharging bottom valve 16, discharging the residual solution and the crystallized crystals into a centrifugal machine 6 of a centrifugal crystallization part, and starting and centrifuging the centrifugal machine 6 to obtain a zinc sulfate product; preferably, in this embodiment, when the crystallization concentration reaches 75 Baume degrees, the residual solution and crystals in the two-way crystallization tank 2 are discharged to the centrifuge 6.
And C and D, centrifuging the residual solution and the crystallized crystals in a centrifuge to obtain zinc sulfate crystals and residual mother liquor, and collecting the separated mother liquor into an external mother liquor barrel through a pipeline.
In addition, the process in this embodiment further includes the following steps:
E. continuously injecting finished product water into the pre-concentration tank 7, recycling primary mixed steam and condensed water output from the secondary steam coil 302 by utilizing the mixed steam gas-liquid separator 14, inputting the separated primary mixed steam into the secondary mixed steam pipe 8, mixing the separated primary mixed steam with secondary steam generated in the evaporation and crystallization process of the secondary crystallization tank 2 to form secondary mixed steam, conveying the secondary mixed steam into the pre-concentration tank 7 through the secondary mixed steam pipe 8, pre-concentrating the finished product water in the pre-concentration tank 7, and stirring the finished product water in the pre-concentration tank 7 by the stirring mechanism 10 to promote full pre-concentration;
F. after the concentration of the finished product water in the pre-concentration tank 7 reaches 30 to 55 Baume degrees, outputting the concentrated finished product water into the first-effect crystallization tank 1 or the second-effect crystallization tank 2 through a pump body and a liquid conveying pipeline between the pre-concentration tank 7 and the first-effect crystallization tank 1 and between the pre-concentration tank 7 and the second-effect crystallization tank 2, and evaporating and crystallizing; preferably, in this embodiment, after the pre-concentration of the product water reaches 40 salmei degrees and the temperature reaches more than 80 ℃, the pre-concentrated product water can be selectively conveyed into the first-effect crystallization tank 1 or the second-effect crystallization tank 2 through the liquid conveying pipeline, the pump body and the valves on the liquid conveying pipeline;
G. and (3) recycling the secondary mixed steam output from the pre-concentration tank 7, and mixing the recycled secondary mixed steam with the secondary mixed steam in the step E through the mixed steam gas-liquid separator 14 and the secondary mixed steam pipe 8 again, and conveying the mixture into the pre-concentration tank 7, so that thorough and full utilization of heat in the steam is realized.
It will be understood that the invention has been described in terms of several embodiments, and that various changes and equivalents may be made to these features and embodiments by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (7)
1. An intermittent evaporation crystallization device adopting two-effect parallel evaporation is characterized in that: the device comprises a first-effect crystallization tank (1) internally provided with a first-effect steam coil pipe (301), a second-effect crystallization tank (2) internally provided with a second-effect steam coil pipe (302), a raw steam recovery part and a centrifugal crystallization part, wherein the first-effect crystallization tank (1) and the second-effect crystallization tank (2) are sealed tank bodies, a raw steam conveying pipe (4) for introducing raw steam generated by an external boiler is arranged on the first-effect crystallization tank (1), and an air inlet of the first-effect steam coil pipe (301) is communicated with the external raw steam conveying pipe (4);
a primary mixed steam pipe (5) communicated with the steam coil pipe in the second-effect crystallization tank (2) is also arranged on the first-effect crystallization tank (1); the air outlet pipe of the raw steam recovery part is communicated with the primary mixed steam pipe (5), and the air inlet pipe is communicated with the outlet of the first-effect steam coil pipe (301);
the feeding end of the centrifugal crystallization part is respectively communicated with the discharging ends of the first-effect crystallization tank (1) and the second-effect crystallization tank (2) through a discharge bottom valve (16);
the device also comprises a pre-concentration tank (7) and a mixed steam recovery part, wherein a pre-concentration steam coil pipe (303) is arranged in the pre-concentration tank, and a secondary mixed steam pipe (8) communicated with the air inlet end of the pre-concentration steam coil pipe (303) is arranged on the secondary crystallization tank (2);
the air inlet pipe of the mixed steam recovery part is respectively communicated with the secondary mixed steam pipe (8) and the air outlet pipe of the two-effect steam pipe coil (302) and the pre-concentration steam pipe coil (303);
the mixed steam recovery part comprises a mixed steam gas-liquid separator (14), and a condensate liquid outlet end of the mixed steam gas-liquid separator (14) is communicated with an external steam boiler through a steam condensate water pipe (17).
2. The intermittent evaporative crystallization device adopting two-effect parallel evaporation according to claim 1, wherein the device is characterized in that: the feed end of the pre-concentration tank (7) is communicated with external finished product water through a finished product water feed pipe (9), and the discharge end of the pre-concentration tank (7) is communicated with feed inlets of the first-effect crystallization tank (1) and the second-effect crystallization tank (2) through a pump body, a liquid conveying pipeline and a valve body arranged on the liquid conveying pipeline respectively.
3. The intermittent evaporative crystallization device adopting two-effect parallel evaporation according to claim 1, wherein the device is characterized in that: stirring mechanisms (10) are arranged in the first-effect crystallization tank (1), the second-effect crystallization tank (2) and the pre-concentration tank (7).
4. The intermittent evaporative crystallization device adopting two-effect parallel evaporation according to claim 1, wherein the device is characterized in that: the raw steam recovery part comprises a raw steam gas-liquid separator (13), and a condensate liquid outlet end of the raw steam gas-liquid separator (13) is communicated with an external steam boiler through a steam condensate water pipe (17).
5. A two-effect parallel evaporation intermittent evaporation crystallization process is characterized in that: the method comprises the following steps of the process,
A. injecting a solution to be crystallized into the tank bodies of the first-effect crystallization tank (1) and the second-effect crystallization tank (2), conveying raw steam into the first-effect crystallization tank (1), stirring the solution in the first-effect crystallization tank (1), and evaporating and crystallizing the solution;
B. recovering the raw steam output from the first-effect crystallization tank (1), mixing the recovered raw steam with secondary steam generated in the evaporation and crystallization process of the first-effect crystallization tank (1) to form primary mixed steam, conveying the primary mixed steam into the second-effect crystallization tank (2), stirring the solution in the second-effect crystallization tank (2), and performing evaporation and crystallization on the solution by utilizing the primary mixed steam;
C. discharging the solution in the first-effect crystallization tank (1) to a centrifugal crystallization part after the concentration of the solution in the first-effect crystallization tank reaches 60-85 Baume degrees, and centrifuging to obtain a product;
D. and discharging the solution in the two-effect crystallization tank (2) to a centrifugal crystallization part after the concentration of the solution in the two-effect crystallization tank reaches 60-85 Baume degrees, and centrifuging to obtain a product.
6. The intermittent evaporative crystallization process adopting two-effect parallel evaporation according to claim 5, wherein the process is characterized in that: it also comprises the steps of,
E. continuously injecting finished product water into a pre-concentration tank (7), recovering primary mixed steam output from a secondary crystallization tank (2), mixing the recovered primary mixed steam with secondary steam generated in the evaporation and crystallization process of the secondary crystallization tank (2) to form secondary mixed steam, conveying the secondary mixed steam into the pre-concentration tank (7), stirring the finished product water in the pre-concentration tank (7), and continuously pre-concentrating the finished product water in the pre-concentration tank (7) by utilizing the secondary mixed steam;
F. after the concentration of the product water reaches 30 to 55 Baume degrees, the product water is injected into a first-effect crystallization tank (1) or a second-effect crystallization tank (2) for evaporation and crystallization;
G. and E, recycling the secondary mixed steam output from the pre-concentration tank (7), and mixing the recycled secondary mixed steam with the secondary mixed steam in the step E again and conveying the mixture to the pre-concentration tank (7).
7. The batch evaporative crystallization process using two-effect parallel evaporation according to claim 6, wherein: the raw steam, the primary mixed steam and the secondary mixed steam are recovered after gas-liquid separation.
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