U.S. patent application number 17/001465 was filed with the patent office on 2021-06-24 for method and system for treating high salinity water.
The applicant listed for this patent is Jinzheng Eco-Technology Co. Ltd.. Invention is credited to Guoliang LI, Hui LI, Yuebiao LI, Huijie LIN, Changyin WAN, Hongzhi YAN, Zhuo ZHANG.
Application Number | 20210188668 17/001465 |
Document ID | / |
Family ID | 1000005049110 |
Filed Date | 2021-06-24 |
United States Patent
Application |
20210188668 |
Kind Code |
A1 |
LI; Yuebiao ; et
al. |
June 24, 2021 |
METHOD AND SYSTEM FOR TREATING HIGH SALINITY WATER
Abstract
The present application is relate to a method and system for
treating high salinity water, comprising the following steps: step
1, by a first membrane concentration unit, concentrating the raw
water; step 2, with the assistance of a crystallization initiation
unit, mixing the raw water concentrated, initiating crystallization
by a seed crystal, and, discharging precipitated crystals; step 3,
with the assistance of a crystallization termination unit, firstly,
introducing the resulting water of the crystallization initiation
unit, then, terminating crystallization, secondly, discharging
precipitated miscellaneous salts; step 4, with the assistance of a
mechanical filter unit, the liquid to discharged from the
crystallization termination unit flowing through the mechanical
filter unit, removing the residual seed crystal and floccules; step
6, with the assistance of a second membrane concentration unit, the
concentrated salinity water entering the second membrane
concentration unit for concentration.
Inventors: |
LI; Yuebiao; (YANTAI,
CN) ; LIN; Huijie; (YANTAI, CN) ; LI; Hui;
(YANTAI, CN) ; LI; Guoliang; (YANTAI, CN) ;
YAN; Hongzhi; (YANTAI, CN) ; WAN; Changyin;
(YANTAI, CN) ; ZHANG; Zhuo; (YANTAI, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jinzheng Eco-Technology Co. Ltd. |
YANTAI |
|
CN |
|
|
Family ID: |
1000005049110 |
Appl. No.: |
17/001465 |
Filed: |
August 24, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F 2001/5218 20130101;
C02F 1/265 20130101; C02F 9/00 20130101; C02F 1/52 20130101 |
International
Class: |
C02F 1/52 20060101
C02F001/52; C02F 1/26 20060101 C02F001/26; C02F 9/00 20060101
C02F009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 18, 2019 |
CN |
201911305489.2 |
Claims
1. A method for treating high salinity water, comprising: firstly,
introducing raw water after pretreatment, and initiating
crystallization of the raw water by crystal seeding method; then,
discharging precipitated crystals, and introducing first resulting
water obtained after precipitating crystals to a next procedure;
thirdly, introducing the first resulting water obtained after
precipitating crystals, and performing miscellaneous salts
precipitation treatment; subsequently, discharging precipitated
miscellaneous salts, and introducing second resulting water
obtained after precipitating miscellaneous salts to another next
procedure; the method specifically comprising: Step 1: performing
pretreatment by a first membrane concentration unit and
concentrating the raw water until degree of supersaturation is more
than 100%; Step 2: with the assistance of a crystallization
initiation unit, firstly, mixing and then introducing the raw water
concentrated in the step 1 into the crystallization initiation
unit; then, initiating crystallization by a seed crystal; and,
discharging the precipitated crystals; Step 3: with the assistance
of a crystallization termination unit, firstly, introducing the
first resulting water of the crystallization initiation unit
obtained after the treatment of the step 2 into the crystallization
termination unit; then, adding a crystallization terminating agent
to terminate crystallization and decreasing the degree of
supersaturation to below 100%; secondly, discharging the
precipitated miscellaneous salts; Step 4: with the assistance of a
mechanical filter unit, liquid discharged from the crystallization
termination unit in the step 3 flowing through the mechanical
filter unit, removing residual seed crystal and floccules, and
discharging salinity water, wherein the liquid discharged from the
crystallization termination unit in the step 3 is the second
resulting water; Step 5: with the assistance of an inline mixer,
adding a first scale inhibitor in an online mixing manner into the
salinity water discharged from the step 4; Step 6: with the
assistance of a second membrane concentration unit, salinity water
after treatment of the step 5 entering the second membrane
concentration unit for concentration.
2. The method for treating high salinity water of claim 1, wherein
in the step 6, the salinity water is concentrated by the second
membrane concentration unit and then divided into at least a first
path and a second path; the first path of the salinity water flows
back before the crystallization initiation unit and is mixed with
concentrated water from the first membrane concentration unit in
the step 1, and the second path of the salinity water is discharged
into a next-stage concentration system or an evaporation pool; in
the step 2, crystallization is initiated by the seed crystal, and
the crystallization initiation unit comprises a seed crystal
feeding port and a crystal stirring device; the particle size of
the added seed crystal ranges from 200 to 1200 mesh; and, the
crystal stirring device is a helical ribbon stirrer, an anchor
stirrer, a turbine stirrer or a paddle stirrer; in the step 2, the
degree of supersaturation of sparingly-soluble salts in high
salinity water entering the crystallization initiation unit is 100%
to 400%; in the step 3, the crystallization termination unit
comprises a feeding device and a stirring device; in accordance
with water quality of the raw water and process requirements, the
crystallization terminating agent comprises lime, sodium carbonate,
sodium hydroxide, trisodium phosphate and/or disodium hydrogen
phosphate; and, the feeding device is a manipulator, a hopper or a
convertor belt, or the crystallization terminating agent is
prepared into a solution and then added by a pump; in the step 1
and step 6, membrane element used in the membrane concentration
units is a nanofiltration membrane element or a reverse osmosis
membrane element, and the type of the membrane element is
spiral-wound type or disc-tube type; and, the ratio of the first
path of the salinity water to the second path of the salinity water
is 1:1.about.5:1.
3. The method for treating high salinity water of claim 2, wherein
the crystallization termination unit adopts adding softening agent,
flocculation and sedimentation; the sparingly-soluble salts in the
high salinity water are calcium sulfate, magnesium sulfate, calcium
carbonate or magnesium hydroxide.
4. A system for treating high salinity water, used to execute the
method for treating high salinity water of claim 1, comprising a
crystallization initiation unit and a crystallization termination
unit which are successively linked in working procedure; the
crystallization initiation unit in which a seed crystal used for
initiating crystallization of supersaturated sparingly-soluble
salts is added, is provided with an inlet for introducing
pretreated raw water, and is further provided with an outlet for
discharging crystals precipitated and an outlet for discharging
resulting water obtained after precipitating crystals; the
crystallization termination unit, comprises a feeding device for
adding materials for terminating crystallization, and is provided
with an inlet for introducing the resulting water obtained after
precipitating crystals and further provided with at least two
outlets; one of the outlets is used for discharging precipitated
miscellaneous salts, and the other outlets is used for discharging
resulting water obtained after precipitating miscellaneous salts; a
first membrane concentration unit is arranged before the
crystallization initiation unit; a mechanical filter unit, an
inline mixer and a second membrane concentration unit are
successively arranged behind the crystallization termination unit;
the first membrane concentration unit in which a second scale
inhibitor is added, and the first membrane concentration unit has
at least two outlets; after concentration treatment of the first
membrane concentration unit, one of the outlets discharges the
first resulting water, and the other outlets discharges
concentrated water in the first membrane concentration unit for
mixing with concentrated water discharged from the second membrane
concentration unit; the crystallization initiation unit is provided
with a seed crystal feeding port and a crystal stirring device, the
inlet of the crystallization initiation unit is to introduce liquid
obtained after mixing the concentrated water from the first
membrane concentration unit and the concentrated water from the
second membrane concentration unit; the crystallization termination
unit is further provided with a stirring device; in accordance with
water quality of the raw water and process requirements, the
crystallization terminating agent comprises lime, sodium carbonate,
sodium hydroxide, trisodium phosphate or disodium hydrogen
phosphate; the feeding device is a manipulator, a hopper, a
convertor belt or a delivery pump; the mechanical filter unit, for
removing crystal particles and suspended matters in salinity water
discharged from the crystallization termination unit; a pipeline
for concentrated water of the second membrane concentration unit,
of which an inlet is connected to an outlet of the mechanical
filter unit; an outlet of the pipeline for concentrated water of
the second membrane concentration unit is divided into at least two
outlets; one of the outlets of the second membrane concentration
unit is connected to a next-stage concentrator, and the other of
the outlets of the second membrane concentration unit is connected
to a pipeline for concentrated water of the first membrane
concentration unit; the inline mixer used for feeding the first
scale inhibitor is arranged between the mechanical filter and the
second membrane concentration unit.
5. The system for treating high salinity water of claim 4, wherein
in the first membrane concentration unit and the second membrane
concentration unit, membrane elements adopt nanofiltration membrane
elements or reverse osmosis membrane elements; a feeding port for
feeding scale inhibitor is formed on the inline mixer; the
mechanical filter adopts an ultrafiltration membrane, a
microfiltration membrane, a high-density sedimentation tank and a
sand filter, or combinations thereof.
6. The system for treating high salinity water of claim 5, wherein
the crystallization initiation unit, the crystallization
termination unit, the first membrane concentration unit, the
mechanical filter unit, and the second membrane concentration unit
are connected by pipelines; in the first membrane concentration
unit and the second membrane concentration unit, the membrane
elements are of spiral-wound type or disc-tube type.
7. The system for treating high salinity water of claim 6, wherein
the pore size of the ultrafiltration membrane ranges from 0.05 to
0.1 .mu.m; and the pore size of the microfiltration membrane ranges
from 0.1 to 0.4 .mu.m.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Chinese
application serial No. CN201910322863.3 filed on Dec. 18, 2019, the
content of which is hereby incorporated herein by reference in its
entirety.
TECHNICAL FIELD
[0002] The present application relates to a method and system for
treating high salinity water.
BACKGROUND OF THE PRESENT INVENTION
[0003] The waste gas produced in thermal power plants and coal
chemical plants generally contains sulfur dioxide. A conventional
treatment method is wet flue gas desulfurization (FGD) using
limestone. The wastewater produced during FGD contains a high
concentration of sulfate radical. Due to its high salt
concentration and complex composition, FGD wastewater is one kind
of industrial wastewater that is difficult to treat. Drainage water
of some coal mines has high salt content, particularly high sulfate
content, due to geological structure; direct discharging of such
drainage water will cause pollution to the environment. The high
salinity water with high sulfate content is generally treated by a
chemical method (neutralization-flocculation-sedimentation), but
the resulting water obtained after the chemical treatment still
contains a high concentration of inorganic salts and other
pollutants, and will pollute the environment once discharged. With
the focus on environmental protection in China, the discharging of
the FGD wastewater is getting more and more strictly or even zero
liquid discharge (ZLD) requirements is required under some
conditions.
[0004] Due to its advantages of high level of automation, small
ground occupation, high treatment efficiency, stable water quality
of the resulting water and the like, reverse osmosis technology is
widely applied in the deep treatment of FGD wastewater and drainage
water of coal mines. However, the high concentration of
sparingly-soluble salts in the FGD wastewater and the drainage
water of coal mines make it easy to form scales on the membrane
surface during reverse osmosis process, thus reduce the treatment
efficiency of the system and even cause the system to break down
quickly. Therefore, it is imperative to develop a reverse osmosis
membrane combined process that can ensure the long-term stable
operation of a reverse osmosis system during the treatment of FGD
wastewater.
[0005] CN105753018A disclosed a device and method for removing
sodium sulfate in salinity water. In this method, a
normal-temperature crystallization system and a membrane
concentrator connected to the normal-temperature crystallization
system are used. The normal-temperature crystallization system
includes a buffer tank, a delivery pump, a heat exchanger and a
normal-temperature crystallizer. This patent introduces a method of
concentrating sodium sulfate in the salinity water to be
supersaturated. The concentration polarization on the membrane
element surface is reduced by adjusting the flow rate and pressure
of the salinity water on the membrane surface during concentration
by the membrane concentrator. Sodium sulfate crystals are obtained
by a normal-temperature crystallization method. The purpose of this
patent is to concentrate sodium sulfate in the salinity water to be
supersaturated by the membrane concentrator, and then take a
normal-temperature crystallization method to crystallize the
supersaturated sodium sulfate. However, when this method is used to
treat high-salinity wastewater in power plants and coal chemical
plants, sparingly-soluble salts (e.g., calcium sulfate, magnesium
hydroxide, calcium carbonate, magnesium sulfate, etc.) will form
scales on the membrane surface, thus the membrane flux is reduced
quickly or even the system will break down, and both the operation
and maintenance cost of the system are increased.
[0006] CN108623034A disclosed a method and system for treating
high-salinity wastewater. The system includes three parts, i.e., a
normal-temperature crystallizer, a filter and a membrane
concentrator. Part of the concentrated water from the membrane
concentrator flows back to the normal-temperature crystallizer to
mix with the raw water; thus improve the degree of supersaturation
of insoluble inorganic salts in the raw water. In this method, by
adding a softening agent and a flocculating agent in the
normal-temperature crystallizer, some inorganic salts are
precipitated in the form of miscellaneous salts; the miscellaneous
salts contain many organic substances such as the flocculating
agent. Most of the miscellaneous salts are useless due to their low
purity, and should be treated as solid wastes. Meanwhile, since the
insoluble inorganic salts are all treated by the softening agent
and the flocculating agent, dosage of agents is high, causing a
high cost of treatment process. This method is characterized in
that crystallization and membrane separation are combined. However,
in this method, during crystallization of inorganic salts,
normal-temperature crystallization is initiated by directly adding
the softening agent to and the flocculating agent, causing high
agent consumption and the treatment cost. Moreover, the obtained
miscellaneous salts is difficultly to be used as industrial salts
due to their low purity, and can only be treated as solid wastes,
which increasing the treatment cost.
[0007] In the existing patents involving the treatment of
high-salinity wastewater, particularly in which involving the
combination with membrane systems, the long-term stable operation
of the membrane systems has not been fully considered. During the
salt removal process, the economic indicators of the salt removal
methods are not considered in most patents, a large amount of
agents is used, while a large amount of miscellaneous salts is
produced, and the treatment cost is high. Up to now, there is no
cost-effective treatment method which can minimize the production
of miscellaneous salts while obtaining pure crystal products on the
basis of ensuring the stable operation of a membrane system.
SUMMARY OF THE PRESENT INVENTION
[0008] The problem to be solved by the present application is to
provide a method and system for treating high salinity water.
[0009] To solve the above problems, the technical solution of the
present application is as follows.
[0010] The purpose of the present application is to overcome the
problem that for high salinity water, the existing treatment cost
is high, high purity salt cannot be obtained, and the operation of
the membrane system is unstable.
[0011] In order to solve the disadvantages of a large amount of
non-additional-value solid precipitates brought by conventional
softening and flocculation, high processing costs, and the problem
of the scaling of the membrane system caused by direct
concentration of the produced water in the triple tank,
[0012] a method for treating high salinity water, firstly,
introducing raw water after pretreated, and initiating
crystallization of the raw water by crystal seeding method; then,
discharging precipitated crystals, and introducing resulting water
obtained after precipitating crystals to a next procedure; thirdly,
introducing the resulting water to obtained after precipitating
crystals, and performing miscellaneous salts precipitation
treatment; subsequently, discharging precipitated miscellaneous
salts, and introducing resulting water obtained after precipitating
miscellaneous salts to a next procedure.
[0013] As a further improvement of the above technical
solution:
[0014] Step 1: performing pretreatment by a first membrane
concentration unit and concentrating the raw water until degree of
supersaturation is more than 100%;
[0015] Step 2: with the assistance of a crystallization initiation
unit, firstly, mixing and then introducing the raw water
concentrated in the step 1 into the crystallization initiation
unit; then, initiating crystallization by a seed crystal; and,
discharging the precipitated crystals;
[0016] Step 3: with the assistance of a crystallization termination
unit, firstly, introducing resulting water of the crystallization
initiation unit obtained after the treatment of the step 2 into the
crystallization termination unit; then, adding a softening agent
and/or a flocculating agent to terminate crystallization and
decreasing the degree of supersaturation to below 100%; secondly,
discharging the precipitated miscellaneous salts;
[0017] Step 4: with the assistance of a mechanical filter unit,
liquid discharged from the crystallization termination unit in the
step 3 flowing through the mechanical filter unit, removing
residual seed crystal and floccules, and discharging salinity
water;
[0018] Step 6: with the assistance of a second membrane
concentration unit, resulting water after treatment of the step 5
entering the second membrane concentration unit for
concentration.
[0019] Step 5 is arranged between the step 4 and step 6, with the
assistance of an online mixer, adding a scale inhibitor in an
online mixing manner; firstly, adding the scale inhibitor into the
salinity water discharged from the mechanical filter unit in the
step 4; and then, executing the step 6.
[0020] In the step 6, the salinity water is concentrated by the
second membrane concentration unit and then divided into at least
two paths; one path of the salinity water is flow back before the
crystallization initiation unit and mixed with the concentrated
water from the first membrane concentration unit in the step 1, and
the other path of the salinity water is discharged into a
next-stage concentration system or an evaporation pool;
[0021] in the step 2, crystallization is initiated by a seed
crystal, and the crystallization initiation unit comprises a seed
crystal feeding port and a crystal stirring device; the particle
size of the added seed crystal ranges from 200 to 1200 mesh; and,
the crystal stirring device is a helical ribbon stirrer, an anchor
stirrer, a turbine stirrer or a paddle stirrer;
[0022] in the step 2, the degree of supersaturation of
sparingly-soluble salts in high salinity water entering the
crystallization initiation unit is 100% to 400%;
[0023] in the step 3, the crystallization termination unit
comprises a feeding device and a stirring device; in accordance
with water quality of the raw water and process requirements,
crystallization terminating agent comprises lime, sodium carbonate,
sodium hydroxide, trisodium phosphate and/or disodium hydrogen
phosphate; and, the feeding device is a manipulator, a hopper or a
convertor belt, or the softening agent and the flocculating agent
are prepared into a solution and then added by a pump;
[0024] in the step 4, the mechanical filter unit is an ultra
filtration membrane, a microfiltration membrane, a high-density
sedimentation tank and a sand filter, or combinations thereof;
[0025] in the step 1 and step 6, membrane element used in the
membrane concentration units is a nanofiltration membrane element
or reverse osmosis membrane element, and the type of the membrane
element is spiral-wound type or disc-tube type; and, the ratio of
the salinity water flowing back to the salinity water discharged in
the second membrane concentration unit is 1:1.about.5:1.
[0026] The crystallization termination unit adopts adding softening
agent, flocculation and sedimentation;
[0027] the ratio of the salinity water flowing back to the salinity
water discharged in the second membrane concentration unit is
1:1.about.5:1;
[0028] the sparingly-soluble inorganic salts in the high salinity
water are calcium sulfate, magnesium sulfate, calcium carbonate or
magnesium hydroxide.
[0029] A system for treating high salinity water, used to execute
the method for treating high salinity water, comprising a
crystallization initiation unit and a crystallization termination
unit which are successively linked in working procedure;
[0030] the crystallization initiation unit in which a seed crystal
used for initiating crystallization of supersaturated
sparingly-soluble salts is added, is provided with an inlet for
introducing pretreated raw water, and is further provided with an
outlet for discharging crystals precipitated and an outlet for
discharging resulting water obtained after precipitating
crystals;
[0031] the crystallization termination unit, comprises a feeding
device for adding materials for precipitating miscellaneous salts,
and is provided with an inlet for introducing the resulting water
obtained after precipitating crystals and further provided with at
least two outlets; one of the outlets is used for discharging
precipitated miscellaneous salts, and the other outlets is used for
discharging resulting water obtained after precipitating
miscellaneous salts.
[0032] As a further improvement of the above technical
solution:
[0033] a first membrane concentration unit is arranged before the
crystallization initiation unit;
[0034] a mechanical filter unit, an online mixer and a second
membrane concentration unit are successively arranged behind the
crystallization termination unit;
[0035] the first membrane concentration unit in which a scale
inhibitor is added, and the first membrane concentration unit has
at least two outlets; after the concentration treatment of the
first membrane concentration unit, one of the outlets discharges
resulting water, and the other outlets discharges concentrated
water in the first membrane concentration unit for mixing with
concentrated water discharged from the second membrane
concentration unit;
[0036] the crystallization initiation unit is provided with a seed
crystal feeding port and a crystal stirring device, the inlet of
the crystallization initiation unit introducing liquid obtained
after mixing the concentrated water from the first membrane
concentration unit and the concentrated water from the second
membrane concentration unit;
[0037] the crystallization termination unit is further provided
with a stirring device and a feeding device for feeding materials
such as a softening agent and/or a flocculating agent; in
accordance with water quality of the raw water and process
requirements, crystallization terminating agent comprises lime,
sodium carbonate, sodium hydroxide, trisodium phosphate or disodium
hydrogen phosphate; the feeding device is a manipulator, a hopper,
a convertor belt or a delivery pump;
[0038] the mechanical filter unit, for removing crystal particles
and suspended matters in salinity water discharged from the
crystallization termination unit;
[0039] a pipeline for concentrated water of the second membrane
concentration unit, of which an inlet is connected to an outlet of
the mechanical filter unit; an outlet of the pipeline for
concentrated water of the second membrane concentration unit is
divided at least two path; one of the outlets is connected to a
next-stage concentrator, and the other outlets is connected to a
pipeline for concentrated water of the first membrane concentration
unit;
[0040] the online mixer used for feeding scale inhibitor is
arranged between the mechanical filter and the second membrane
concentration unit.
[0041] In the first membrane concentration unit and the second
membrane concentration unit, membrane elements of the membrane
concentration units adopt nanofiltration membrane elements or
reverse osmosis membrane elements;
[0042] a feeding port for feeding scale inhibitor is formed on the
online mixer;
[0043] the mechanical filter adopts an ultrafiltration membrane, a
microfiltration membrane, a high-density sedimentation tank and a
sand filter, or combinations thereof.
[0044] Each of the units is connected by pipelines;
[0045] the membrane element is of spiral-wound type or disc-tube
type.
[0046] The pore size of the ultrafiltration membrane range from
0.05 to 0.1 .mu.m; while, the pore size of the microfiltration
membrane ranges from 0.1 to 0.4 .mu.m.
[0047] Compared with the prior art (e.g., CN108623034A, etc.), the
present application mainly differs in that, in the present
application, crystallization is initiated by crystal seeding
method, and a crystallization initiation region and a
crystallization termination region are divided as two independent
regions. Since crystallization initiated by crystal seeding method
is selective, high-purity crystals with additional value can be
obtained in a crystallization initiation unit. Crystallization can
be terminated just by adding a small amount of a softening agent in
a crystallization termination unit, and the degree of
supersaturation of sparingly-soluble salts in the salinity water is
reduced to below 100%, during this process, only a small amount of
miscellaneous salts to be discharged as sludge is produced.
However, in CN108623034A, the inorganic salts in the concentrated
solution are precipitated by directly adding a flocculating agent
and a softening agent, a large amount of the softening agent and
the flocculating agent will be used in this method, the
precipitated inorganic salts are almost present in the form of
miscellaneous salts, and the miscellaneous salts are useless and
can only be further treated as solid wastes.
[0048] In the present application, crystallization initiated by
crystal seeding method is innovatively combined with a membrane
system, and the concentrated water is softened before entering the
membrane system, ensuring that the salinity water can be highly
concentrated in the membrane system without forming scales. The
highly-concentrated water is flow back before the crystallization
initiation unit and mixed with the concentrated water from the
first membrane concentration unit, so it ensured that the
concentrated water entering the crystallization unit has a high
degree of supersaturation, the concentrating process of the
concentrated water before the crystallization initiation unit is
reduced, and the system investment is reduced. Since
crystallization and softening processes are performed at different
stages, the deep softening effect can be achieved just by adding a
small amount of the softening agent in the softening stage, so that
the cost for agents is greatly reduced, and the amount of sludge
produced is decreased, it is ensured that the membrane concentrator
can highly concentrate the salinity water, and the TDS of the
salinity water entering a next-stage system can reach 80000 to
120000 ppm or even 130000 ppm in extreme cases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1 is a schematic structure diagram of the method and
system of one implementation according to the present
application;
[0050] FIG. 2 is a schematic structure diagram of the method and
system of one implementation according to the present
application.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0051] In the following, the present application will be described
in detail through exemplary implementations. However, it should be
understood, without further recitation, the elements, structure and
features in one implementation may be beneficially combined in
other implementations without further recitation.
[0052] In the description of the present application, it is to be
noted that terms "first", "second" are used for descriptive
purposes and should not be interpreted to indicate or imply the
relative importance. In addition, the term "and/or" in the
implementations of this application describes only an association
relationship between associated objects and represents that three
relationships may exist. For example, A and/or B may represent the
following three cases: only A exists, both A and B exist, and only
B exists. In addition, the character "/" in this specification
usually indicates an "or" relationship between associated
objects.
[0053] As shown in FIG. 1, the method for treating high salinity
water in this implementation comprises the following steps.
Firstly, raw water after pretreated is introduced, and
crystallization of the raw water is initiated by crystal seeding
method. Then, precipitated crystals are discharged, and resulting
water obtained after precipitating crystals is introduced to a next
procedure. Thirdly, introduce the resulting water obtained after
precipitating crystals, and perform miscellaneous salts
precipitation treatment. Subsequently, precipitated miscellaneous
salts are discharged, and resulting water obtained after
precipitating miscellaneous salts is introduced to a next
procedure.
[0054] Specifically, in one implementation, the method may comprise
the following steps.
[0055] Step 1: Pretreatment is performed by a first membrane
concentration unit, and the raw water is concentrated until degree
of supersaturation is more than 100%.
[0056] Step 2: With the assistance of a crystallization initiation
unit, firstly, the raw water concentrated in the step 1 is mixed
and introduced into the crystallization initiation unit; then,
crystallization is initiated by crystal seeding method; and, the
precipitated crystals are discharged.
[0057] Step 3: With the assistance of a crystallization termination
unit, firstly, resulting water of the crystallization initiation
unit obtained after the treatment of the step 2 is introduced into
the crystallization termination unit; then, a softening agent
and/or a flocculating agent is added to terminate crystallization
process and the degree of supersaturation is decreased to below
100%; secondly, the precipitated miscellaneous salts are
discharged.
[0058] Step 4: With the assistance of a mechanical filter unit,
liquid discharged from the crystallization termination unit in the
step 3 flows through the mechanical filter unit, residual seed
crystal and floccules are removed, and salinity water is
discharged.
[0059] Step 6: With the assistance of a second membrane
concentration unit, salinity water after treatment of the step 5
enters the second membrane concentration unit for
concentration.
[0060] Step 5 is provided between the step 4 and step 6. In the
step 5, with the assistance of an online mixer, a scale inhibitor
is added in an online mixing manner; firstly, the scale inhibitor
is added into the salinity water discharged from the mechanical
filter unit in the step 4; and then, the step 6 is executed.
[0061] In the step 6, the salinity water is concentrated by the
second membrane concentration unit and then divided into at least
two paths; one path of the salinity water is flow back before the
crystallization initiation unit and mixed with concentrated water
from the first membrane concentration unit in the step 1, and the
other path of the salinity water is discharged into a next-stage
concentration system or an evaporation pool.
[0062] In the step 2, crystallization process is initiated by a
crystal seeding method, and the crystallization initiation unit
comprises a seed crystal feeding port and a crystal stirring
device; the particle size of the added seed crystal ranges from 200
to 1200 mesh; and, the crystal stirring device is a helical ribbon
stirrer, an anchor stirrer, a turbine stirrer or a paddle
stirrer.
[0063] In the step 2, the degree of supersaturation of
sparingly-soluble salts in high salinity water entering the
crystallization initiation unit is 100% to 400%. That is, after the
pretreatment of the first membrane concentration unit, in the raw
water, the degree of supersaturation of the sparingly-soluble salts
is 100% to 400%, the raw water has become the high salinity
water.
[0064] In the step 3, the crystallization termination unit
comprises a feeding device and a stirring device; in accordance
with water quality of the raw water and process requirements,
crystallization terminating agent comprises lime, sodium carbonate,
sodium hydroxide, trisodium phosphate and/or disodium hydrogen
phosphate; and, the feeding device is a manipulator, a hopper or a
convertor belt, or the softening agent and the flocculating agent
are prepared into a solution and then added by a pump.
[0065] In the step 4, the mechanical filter unit is an ultra
filtration membrane, a microfiltration membrane, a high-density
sedimentation tank and a sand filter, or combinations thereof.
[0066] In the step 1 and step 6, membrane elements used in the
membrane concentration units are nanofiltration membrane elements
or reverse osmosis membrane elements, and the type of the membrane
element is spiral-wound type or disc-tube type; and, the ratio of
the salinity water flowing back to the salinity water discharged in
the second membrane concentration unit is 1:1.about.5:1. That is,
in step 6, the ratio of the salinity water mixing with the
concentrated water obtained in step 1 to the salinity water
discharged into a next-stage is 1:1.about.5:1.
[0067] The crystallization termination unit may adopt method of
softening, flocculation and sedimentation;
[0068] the ratio of the salinity water flowing back to the salinity
water discharged in the second membrane concentration unit is
1:1.about.5:1;
[0069] the sparingly-soluble salts in the high salinity water are
calcium sulfate, magnesium sulfate, calcium carbonate or magnesium
hydroxide.
[0070] The system for treating high salinity water in this
implementation is used to execute the method for treating high
salinity water, and comprises a crystallization initiation unit 1
and a crystallization termination unit 2 which are successively
linked in working procedure.
[0071] The crystallization initiation unit 1 in which a seed
crystal used for initiating crystallization of supersaturated
sparingly-soluble salts is added, is provided with an inlet 101 for
introducing pretreated raw water, and is further provided with an
outlet 102 for discharging crystals precipitated and an outlet 103
for discharging resulting water obtained after precipitating
crystals.
[0072] The crystallization termination unit 2, comprises a feeding
device 21 for adding materials for precipitating miscellaneous
salts, and is provided with an inlet 201 for introducing the
resulting water obtained after precipitating crystals and further
provided with at least two outlets; one of the outlets 202 is used
for discharging precipitated miscellaneous salts, and the other
outlets 203 is used for discharging resulting water obtained after
precipitating miscellaneous salts.
[0073] A first membrane concentration unit 3 is arranged before the
crystallization initiation unit 1;
[0074] a mechanical filter unit 4, an online mixer 5 and a second
membrane concentration unit 6 are successively arranged behind the
crystallization termination unit 2;
[0075] the first membrane concentration unit 3 in which the scale
inhibitor is added, and the first membrane concentration unit has
at least two outlets 301, 302; after concentration treatment of the
first membrane concentration unit, one of the outlets 301
discharges resulting water, and the other outlets 302 discharges
concentrated water in the first membrane concentration unit, which
is to be mixed with concentrated water discharged from the second
membrane concentration unit 6;
[0076] the crystallization initiation unit 1 is provided with a
seed crystal feeding port 11 and a crystal stirring device 12, the
inlet 101 of the crystallization initiation unit is to introduce
liquid obtained after mixing the concentrated water from the first
membrane concentration unit 3 and the concentrated water from the
second membrane concentration unit 6;
[0077] the crystallization termination unit 2 is further provided
with a stirring device 22 and a feeding device 21 for feeding
materials such as a softening agent and/or a flocculating agent; in
accordance with water quality of the raw water and process
requirements, crystallization terminating agent comprises lime,
sodium carbonate, sodium hydroxide, trisodium phosphate or disodium
hydrogen phosphate; the feeding device 21 is a manipulator, a
hopper, a convertor belt or a delivery pump;
[0078] the mechanical filter unit 4, for removing crystal particles
and suspended matters in salinity water discharged from the
crystallization termination unit 2;
[0079] a pipeline 7 for concentrated water of the second membrane
concentration unit 6, that is the pipeline for the concentrated
water obtained by the treatment of the second membrane
concentration unit passing through, of which an inlet 601 is
connected to an outlet 401 of the mechanical filter unit 4; an
outlet of the pipeline for concentrated water of the second
membrane concentration unit is divided at least two; one of the
outlets 701 is connected to a next-stage concentrator, and the
other outlets 702 is connected to a pipeline 8 for concentrated
water of the first membrane concentration unit 3;
[0080] the online mixer 5 used for feeding scale inhibitor is
arranged between the mechanical filter 4 and the second membrane
concentration unit 6.
[0081] For the crystallization termination unit, the feeding device
for feeding materials such as a softening agent and/or a
flocculating agent and the feeding device for adding materials for
precipitating miscellaneous salts may be the same one which can be
seen from FIG. 2, or two independent feeding devices.
[0082] The second membrane concentration unit 6 is further provided
with an outlet 602 for discharges the resulting water obtained
after the treatment of this unit.
[0083] In the first membrane concentration unit 3 and the second
membrane concentration unit 6, membrane elements may adopt
nanofiltration membrane elements or reverse osmosis membrane
elements;
[0084] a feeding port 501 for feeding scale inhibitor is formed on
the online mixer;
[0085] the mechanical filter 4 may adopt an ultrafiltration
membrane, a microfiltration membrane, a high-density sedimentation
tank and a sand filter, or combinations thereof.
[0086] Each of the units is connected by pipelines.
[0087] The membrane element is of spiral-wound type or disc-tube
type.
[0088] The pore size of the ultrafiltration membrane range from
0.05 to 0.1 .mu.m; and the pore size of the microfiltration
membrane ranges from 0.1 to 0.4 .mu.m.
[0089] Specifically, the present application provides a method for
treating high salinity water. The method comprises providing an
independent crystallization initiation unit and an independent
crystallization termination unit, the crystallization condition is
explicitly defined as crystal seeding method, and the
crystallization is initiated by adding a seed crystal; the particle
size of the seed crystal ranges from 200 to 1200 mesh, preferably
400 to 1000 mesh; the temperature of the crystallization initiation
unit is controlled to be 10.degree. C. to 40.degree. C. In the
crystallization termination unit, by adding the softening agent and
the flocculating agent, the crystallization initialized by the seed
crystal is terminated, and the hardness of the resulting water is
also reduced. The softening agent selected is one of or a
combination of sodium carbonate, sodium hydroxide and calcium
hydroxide, and the temperature of the crystallization termination
unit is controlled to be 10.degree. C. to 40.degree. C. The
inorganic salt contained in the concentrated water may be one of or
a combination of calcium sulfate, magnesium sulfate, calcium
carbonate and magnesium hydroxide. The mechanical filter in the
present application may be an ultrafiltration membrane, a
microfiltration membrane, a high-density sedimentation tank and a
sand filter, or combinations thereof, the specific selection of the
mechanical filter may be comprehensively considered according to
the occupied area of the project, etc. The resulting water of the
crystallization termination unit should be added with the scale
inhibitor before entering the second membrane concentration unit;
the scale inhibitor can be added before or after the mechanical
filter, preferably after the mechanical filter; the concentration
of the added scale inhibitor is 1 to 50 ppm, preferably 10 to 20
ppm. The first membrane concentration unit and the second membrane
concentration unit may adopt nanofiltration membranes or reverse
osmosis membranes, and the structure type of the membrane element
is spiral-wound type or disc-tube type. Since the disc-tube type
membrane elements have low requirements on the intaking water and
have high scaling and pollution resistance, the disc-tube type
reverse of osmosis membrane and nanofiltration membrane elements
are preferred. If the system is required to have a certain salt
separation function, a nanofiltration membrane is preferred; and,
if the liquid to be treated is relatively simple in composition,
the system is not required to permeate monovalent salts alone, so a
reverse osmosis membrane with higher concentration efficiency is
preferred. In the present application, the crystals obtained in the
crystallization initiation unit are high in purity, and can be
discharged, dried and packaged. A small amount of miscellaneous
salts is obtained by the crystallization termination unit, and the
miscellaneous salts are discharged and treated as solid wastes. The
operating pressure of the membrane concentration unit is 1 MPa to 6
MPa; the operating pressure depends upon the concentration and the
concentration rate of the high salinity water entering the membrane
concentration unit. The operating temperature of the spiral-wound
type membrane element is 5.degree. C. to 45.degree. C., while the
operating temperature of the disc-tube type membrane element is
5.degree. C. to 60.degree. C., the operating temperature is
preferably 20.degree. C. to 35.degree. C. The ratio of the backflow
water to the discharged water of the concentrated water in the
second membrane concentration unit is 1:1 to 5:1, preferably 2:1 to
4:1.
[0090] The system of the present application comprises: a first
membrane concentration unit for concentrating the raw water, and a
crystallization initiation unit for feeding a seed crystal, the raw
water entering the crystallization initiation device is mixed
liquid of the concentrated water from the first membrane
concentration unit and part of the concentrated water from the
second membrane concentration unit; a crystallization termination
unit, which comprises a device for feeding the softening agent and
the flocculating agent and is used for terminating the
crystallization initiated by a seed crystal and softening the
concentrated water; a mechanical filter unit for removing crystals
and suspended matters in the resulting water of the crystallization
termination unit; a scale inhibitor online mixer for feeding scale
inhibitor before the concentrated water enters the membrane system;
and, a second membrane concentration unit in which part of the
concentrated water flows back to the crystallization initiation
unit and part of the concentrated water is discharged to a
next-stage treatment system. The TDS (total dissolved solids) of
the concentrated water entering a next-stage concentrator after
being concentrated by the membrane system may reach 80000 to 120000
ppm, so that the treatment process is greatly shortened and the
energy consumption is saved.
[0091] The high salinity water entering the crystallization
initiation unit contains part of the concentrated water produced by
the second membrane concentration unit to improve the degree of
supersaturation of sparingly-soluble salts in the concentrated
water, so that the cost required for deep concentration of the
salinity water before the crystallization initiation unit is
reduced; a crystallization termination operation needs to be
performed on the resulting water of the crystallization initiation
unit; the crystallization is terminated by adding the softening
agent such as calcium oxide or calcium hydroxide and the
flocculating agent, and the salinity water is softened. The water
from the crystallization termination unit needs to be mechanically
filtered to prevent crystals and suspended matters from polluting
the membrane concentration system.
Embodiment
[0092] Raw water is treated by a first membrane concentration unit
to obtain 70 T/h of high-salinity wastewater having a degree of
calcium sulfate supersaturation of 130%; the high-salinity
wastewater is mixed with 20 T/h of concentrated water having a
degree of calcium sulfate supersaturation of 350% from a membrane
system to obtain 90 T/h of mixed water having a degree of calcium
sulfate supersaturation of 179%; the mixed water is introduced into
a crystallization initiation unit, and a seed crystal calcium
sulfate dehydrate in 500 mesh is added; and the mixed water is
stirred with a helical ribbon stirrer at 50 rpm. Calcium sulfate
crystals are discharged, dried and then packaged.
[0093] The degree of supersaturation of calcium sulfate in the
resulting water in the crystallization initiation unit is 110%, and
the flow is 90 T/h (tons per hour).
[0094] The resulting water of the crystallization initiation unit
enters a crystallization termination unit, a solution of calcium
hydroxide having a mass concentration of 5% and polyacrylamide in
40 ppm is added and stirred by a helical ribbon stirrer at 40 rpm,
and miscellaneous salts are precipitated and discharged. The degree
of supersaturation of calcium sulfate in the resulting water from
the crystallization to termination unit is reduced to 100%.
[0095] The resulting water in the crystallization termination unit
is filtered by an ultrafilter having a pore size of 0.05 .mu.m and
then added with a scale inhibitor of 5 ppm online, and then enters
the second membrane concentration unit.
[0096] 90 T/h of the concentration salinity water enters a DTRO
(Disc-Tube Reverse Osmosis) system, that is a second membrane
concentration unit having a recovery rate of 71.4%, to obtain 64.3
T/h of resulting water having a hardness of 0, and 25.6 T/h of
concentrated water having a degree of calcium sulfate
supersaturation of 350%, 20 T/h of the concentrated water is flow
back before the crystallization initiation unit to mixed with the
raw water, and 5.6 T/h of the concentrated water is discharged to a
next-stage treatment system.
[0097] The present application is reasonable in design, low in
cost, firm and durable, safe and reliable, simple in operation,
compact in stricture, and convenient for automatic control.
* * * * *