[One]The present specification relates to a method for enriching high salt raw water.
[2]
This application claims the benefit of the filing date of Korean Patent Application No. 10-2019-0119618, filed with the Korean Intellectual Property Office on September 27, 2019, the entire contents of which are incorporated herein by reference.
background
[3]
High salt concentration wastewater discharged from oil fields contains a higher concentration of salt than general seawater. Conventionally, high salt concentration wastewater is buried or recycled, but a method of discharging high salt concentration wastewater after purification has been devised due to environmental causes and limitations of recycling sites. Distillation was generally used to purify this high salt concentration wastewater, but such a heat treatment method consumes a lot of energy, so economic efficiency is low. To improve this, technologies such as reverse osmosis, forward osmosis, and membrane distillation are being developed for the treatment of high salt concentration wastewater.
[4]
Osmosis is a phenomenon in which the solvent moves through the separation membrane from a solution with a low solute concentration to a solution with a high solute concentration between two solutions separated by a semipermeable membrane. is called osmotic pressure. However, when an external pressure higher than the osmotic pressure is applied to the high-concentration side, the solvent moves from the high-solute-concentration solution side to the low-solute-concentration solution side. This phenomenon is called reverse osmosis. Using the reverse osmosis principle, it is possible to separate various salts or organic substances through a semipermeable membrane by using a pressure gradient as a driving force. Reverse osmosis membrane using this reverse osmosis phenomenon is used to supply water for home, construction, and industrial use by separating substances at the molecular level and removing salt from salt water or seawater.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[5]
The present specification relates to a method for enriching high salt raw water.
means of solving the problem
[6]
An exemplary embodiment of the present specification provides a high-salt raw water concentration method in which raw water having a concentration of 70,000 ppm or more is passed through a separation membrane at a temperature of 40° C. or less and a pressure of 1,200 psi or less to obtain product water satisfying the following Equation 1.
[7]
[Equation 1]
[8]
N s = B * (C m - C p ),
[9]
In Formula 1, B is a salt transmittance constant (B-value), 3 GFD≤B≤150 GFD,
[10]
N s is the amount of salt that has passed through the separation membrane (GFD * ppm), which is the value of F p * C p ,
[11]
C m is the membrane concentration (ppm) on the raw water side,
[12]
C p is the Permeate concentration (ppm).
[13]
F p is the production water flow rate (Permeate Flux), 5 GFD ≤ Fp ≤ 100 GFD.
Effects of the Invention
[14]
When the high salt raw water is concentrated by the high salt raw water concentration method according to the exemplary embodiment of the present specification, a higher level of concentration effect can be obtained by applying a low raw water pressure, and there is an economic advantage.
Best mode for carrying out the invention
[15]
In the present specification, when a member is said to be located “on” another member, this includes not only a case in which a member is in contact with another member but also a case in which another member is present between the two members.
[16]
In the present specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.
[17]
An exemplary embodiment of the present specification provides a high-salt raw water concentration method in which raw water having a concentration of 70,000 ppm or more is passed through a separation membrane at a temperature of 40° C. or less and a pressure of 1,200 psi or less to obtain product water satisfying the following Equation 1.
[18]
[Equation 1]
[19]
N s = B * (C m - C p ),
[20]
In Formula 1, B is a salt transmittance constant (B-value), 3 GFD≤B≤150 GFD,
[21]
N s is the amount of salt that has passed through the separation membrane (GFD * ppm), which is the value of F p * C p ,
[22]
C m is the membrane concentration (ppm) on the raw water side,
[23]
C p is the Permeate concentration (ppm).
[24]
F p is the production water flow rate (Permeate Flux), 5 GFD ≤ Fp ≤ 100 GFD.
[25]
In the method of purifying high-salt raw water discharged from oil fields, the method using reverse osmosis is more economical than other methods such as forward osmosis and membrane distillation and has the advantage that existing reverse osmosis (RO) facilities can be used. It has a disadvantage that a higher pressure than the osmotic pressure of the raw water must be applied to the raw water side. Since the osmotic pressure is proportional to the concentration, high raw water pressure is required to overcome the high raw water osmotic pressure when treating high salt concentration raw water. When such high raw water pressure is used, an increase in operating cost occurs due to additional energy consumption. In addition, since the existing reverse osmosis (RO) modules are not manufactured to withstand such harsh operating conditions, a separate, expensive special reverse osmosis (RO) module facility is required for operation under such harsh conditions, and additional devices are required accordingly. the cost occurs.
[26]
In the case of osmotically assisted Reverse Osmosis (OARO), which has been recently developed to overcome this problem, it is necessary to continuously inject a high concentration of draw solution to the production water side, and draw solution and reverse osmosis Concentration polarization occurs on the surface of the membrane where the production water is mixed, and there is a disadvantage in that the membrane efficiency is lowered.
[27]
On the other hand, in the case of the high salt raw water concentration method according to the present specification, the osmotic pressure difference between both sides of the separation membrane is reduced by using a separation membrane with a high salt permeability compared to the existing one, and thus, it is possible to concentrate the raw water even at a low operating pressure and obtain a high production water flow rate can That is, the high salt raw water concentration method according to the present specification reduces energy consumption compared to the conventional high salt raw water concentration method through the reverse osmosis process, and has the advantage that it does not require additional facility costs because it can concentrate the high salt raw water using a general reverse osmosis facility. there is.
[28]
The F p (production water flow rate) can be measured by measuring the volume of the product water that has passed through the separation membrane for a certain period of time, and C p (production water concentration) can be measured by a method through conductivity measurement, C m (the surface concentration of the separation membrane on the raw water side) can be measured by measuring the conductivity of the raw water and measuring the recovery rate. Specifically, it is possible to convert the conductivity of raw water and produced water into salt concentration by using the calibration data between conductivity and salt concentration. In addition, the membrane surface concentration can be calculated through the raw water concentration and recovery rate in Equation 3 below.
[29]
[Equation 3]
[30]
C m = k * C f * Rec
[31]
In Equation 3,
[32]
C m is the surface concentration (ppm) of the separation membrane on the raw water side,
[33]
C f is the raw water concentration (ppm),
[34]
k is the experimental constant,
[35]
Rec is the recovery (%).
[36]
The recovery rate is a ratio of the raw water flow rate and the production water flow rate, and can be obtained by the production water flow rate (F p )/the raw water flow rate (F f ). The recovery may be 1% to 80%, preferably 5% to 60%, more preferably 10% to 40%.
[37]
The B (salt transmittance constant (B-value)) is preferably 3 GFD≤B≤150 GFD, more preferably 19 GFD≤B≤43 GFD.
[38]
When the B (salt permeability constant (B-value) satisfies the above-mentioned range, there is an effect of enabling low pressure concentration due to a decrease in osmotic pressure difference. Specifically, in high salt conditions, B value is 3 GFD (80% removal rate, If it is lower than 6,000 GPD flow rate), it is difficult to expect the effect of reducing the osmotic pressure difference because the concentration of produced water is too low. More specifically, when the B value is 19 GFD (50% removal rate, 9,000 GPD flow rate) to 43 GFD (50% removal rate, 20,000 GPD flow rate), more preferably effective osmotic pressure difference reduction effect and concentration effect occurs.
[39]
Specifically, the flow rate of production water passing through a separation membrane such as a reverse osmosis membrane can be calculated using the following Equations 4-1 to 4-3.
[40]
[Equation 4-1]
[41]
F p = A * NDP
[42]
[Equation 4-2]
[43]
NDP = P f -Δπ
[44]
[Equation 4-3]
[45]
Δπ = π f - π p
[46]
In Formulas 4-1 to 4-3,
[47]
F p is the production water flow (GFD)
[48]
A is the water permeation constant (A-value), 0.035 GFD/psi≤A≤0.10 GFD/psi,
[49]
NDP is Net Driving Pressure (psi),
[50]
P f is the feed pressure (psi),
[51]
π is the osmotic pressure (psi),
[52]
π f is the feed osmotic pressure (psi),
[53]
π p is the permeate osmotic pressure (psi) of the production water,
[54]
Δπ is the difference (psi) between the osmotic pressure of the produced water and the osmotic pressure of the raw water.
[55]
That is, in order to obtain produced water, a source water pressure exceeding the osmotic pressure difference between the source water and the produced water must be applied to the source water side, and the produced water flow rate is proportional to the net driving pressure (NDP), which is the difference between the source water pressure and the osmotic pressure difference.
[56]
In the present specification, the concentration of produced water is increased by using a filter having a high salt permeability compared to the prior art, and thus the osmotic pressure difference is reduced, resulting in a high Net Driving Pressure (NDP) even at a low raw water pressure compared to the prior art, and as a result, a high production water flow rate can get
[57]
Referring to Equation 5 below, since the concentrated water flow rate is lowered when the production water flow rate is increased, there is an advantage that the concentrated water flow rate to be discarded can be reduced even at low raw water pressure.
[58]
[Equation 5]
[59]
F f = F p + F c
[60]
In Equation 5,
[61]
F f is the raw water flow (GFD),
[62]
F p is the production water flow rate (GFD),
[63]
F c is the brine flow rate (GFD).
[64]
In order to increase the production water flow rate and decrease the concentrated water flow rate according to Equation 5 above, it is necessary to increase the Net Driving Pressure (NDP). There are two methods for raising the NDP (Net Driving Pressure): raising the raw water pressure and lowering the osmotic pressure.
[65]
In the existing water treatment method using reverse osmosis, a separation membrane with a high salt removal rate of 99% or more was used to obtain a low concentration of produced water, and to overcome the osmotic pressure, the raw water pressure higher than the raw water osmotic pressure was applied to the separation membrane to increase the production water flow rate.
[66]
The high salt raw water concentration method according to the present specification is different from the conventional reverse osmosis method in that high net driving pressure (NDP) is obtained by reducing the osmotic pressure difference instead of applying high raw water pressure.
[67]
Specifically, in the present invention, a separation membrane with high salt permeability is used to increase the concentration of produced water, and accordingly, the osmotic pressure of the produced water is increased to reduce the osmotic pressure difference between the separation membranes, thereby obtaining high Net Driving Pressure (NDP) even at low operating pressure, and ultimately It is possible to obtain a high production water flow rate and a low concentrated water flow rate.
[68]
As a way to overcome the need for high raw water pressure, techniques such as osmotically-assisted RO (OARO) or osmotically-enhanced RO (OERO) inspired by forward osmosis (FO) are being studied recently. In addition to the reverse osmosis system, they inject high-salt water (draw solution) to the production water side to increase the production water concentration, increase the production water osmotic pressure, and lower the osmotic pressure difference between both sides of the separation membrane to achieve high net driving pressure (NDP) even at low raw water pressure. made it possible to get
[69]
However, they continuously need to inject high salt (draw solution) to the production water side during operation. In addition, since the existing reverse osmosis membrane with low salt permeability is used, the low concentration of the production water passing through the separation membrane is mixed with the draw solution on the production water side, and high salt water (draw solution) on the surface of the separation membrane on the production water side It still has the disadvantage of forward osmosis in that the reverse osmosis efficiency is lowered due to the concentration polarization effect that occurs on the side of the produced water due to the lower concentration of .
[70]
On the other hand, the present invention has the advantage of OARO (Osmotically-assisted reverse osmosis), in which high salt raw water concentration is possible even at low pressure due to the high osmotic pressure of the production water, and at the same time, it is free from the disadvantages of the OARO (Osmotically-assisted reverse osmosis).
[71]
In the high salt raw water concentration method according to the present specification, since a high concentration of salt is directly injected from the raw water side to the production water side, there is no need for a separate high salt water (draw solution), and the complicated OARO for injecting the high salt water (draw solution) No need for facilities. That is, the present invention is clearly distinguished from the prior literature in that a separate facility for inputting high salt water into the production water is not required.
[72]
In addition, since the high salt raw water concentration method according to the present specification uses a separation membrane with high salt permeability, the concentration polarization effect on the raw water side is lower than that of the existing reverse osmosis membrane, and the solution flowing through the production water side is only the solution that has passed through the separation membrane Therefore, the dilution effect does not occur on the side of the produced water, and as a result, a lower concentration polarization effect occurs on the side of the produced water compared to forward osmosis (FO) or osmotically assisted reverse osmosis (OARO).
[73]
Therefore, the present invention is characterized in that it is possible to obtain the same level of recovery rate and excellent high-salt raw water concentration effect even when the raw water pressure is low compared to the prior art.
[74]
In the present specification, the raw water is an aqueous solution containing shale gas produced water (Produced water), seawater (SW: Sea water), brackish water, and common salt (NaCl) used in osmosis processes such as industrial water. may be used, and preferably, the raw water may be shale gas production water.
[75]
An exemplary embodiment of the present specification provides a high-salt raw water concentration method wherein the osmotic pressure of the produced water is 15% to 90% of the osmotic pressure of the raw water.
[76]
When the osmotic pressure of the produced water satisfies the above-mentioned range, there is an effect that the low pressure concentration of the high salt raw water is possible due to a decrease in the difference between the osmotic pressure of the produced water and the raw water.
[77]
The difference in osmotic pressure between the raw water and the produced water can be measured by a method of conductivity measurement when the chemical composition of the raw water and the produced water is known.
[78]
In one embodiment of the present specification, the raw water has a concentration of 70,000 ppm or more and 200,000 ppm or less.
[79]
When the raw water concentration satisfies the above range, raw water concentration using a general reverse osmosis membrane is impossible under the general reverse osmosis product operating conditions (800 psi, 25 °C), whereas when using the high salt raw water concentration method, even under normal reverse osmosis operating conditions There is an effect that the concentration of raw water occurs.
[80]
The raw water concentration can be measured by a conductivity measurement method when the chemical composition of the raw water is known.
[81]
In one embodiment of the present specification, the pressure is 400 psi or more and 1,200 psi or less. This means that the above-mentioned pressure is "400 psi or more and 1,200 psi or less" in the above-mentioned "raw water having a concentration of 70,000 ppm or more at a temperature of 40° C. or less and a pressure of 1,200 psi or less".
[82]
Since the pressure satisfies the above range, it is not necessary to apply a high pressure to be applied in a conventional osmosis process, and thus energy required for the osmosis process can be significantly reduced, thereby making it economical.
[83]
In an exemplary embodiment of the present specification, the salt removal rate of the produced water satisfies the following Equation 2, and is 10% to 85%.
[84]
[Equation 2]
[85]
Salt Removal Rate = (1- C p /C f ) * 100
[86]
C p is the permeate concentration (ppm),
[87]
C f is the feed concentration (ppm).
[88]
Preferably, the salt removal rate of the produced water may be 40% to 80%, more preferably 45% to 60%.
[89]
Since the salt removal rate of the produced water satisfies the above range, the osmotic pressure of the produced water is increased to reduce the osmotic pressure difference, and there is an effect of concentrating the high salt raw water under normal reverse osmosis operation conditions.
[90]
To measure the salt removal rate of the produced water, a water treatment module including a plate-type permeation cell, a high-pressure pump, a storage tank, and a cooling device may be used. After the separation membrane is installed in the permeation cell, the preliminary operation is sufficiently performed for about 1 hour using tertiary distilled water to stabilize the evaluation equipment. After confirming that the raw water was stabilized by operating the equipment at a flow rate of 400 psi to 1,200 psi and 4 L/min for about 1 hour, a conductivity meter was used to measure the salt concentration before and after permeation, and the salt removal rate ( %) can be calculated.
[91]
In the present specification, the “salt” of the salt removal rate is typically sodium chloride (NaCl) or magnesium sulfate (MgSO 4 ), and may include other salts. For example, if NaCl raw water having a concentration of 70,000 ppm is concentrated, the salt removal rate in the present specification means the removal rate of NaCl, and if MgSO 4 raw water having a concentration of 70,000 ppm is concentrated, the salt removal rate in this specification means the removal rate of MgSO 4 .
[92]
In one embodiment of the present specification, the flow rate (F p ) per area of ​​the produced water is 5 GFD or more and 100 GFD or less.
[93]
In the flow rate per area, “area” may mean 400 ft 2 or 440 ft 2 .
[94]
In the present specification, GFD is a unit of flow rate, meaning Gallon/ft 2 /day (Gallon per square Foot per Day).
[95]
In the present specification, GPD is a flow rate unit, and means Gallon/day (Gallon Per Day).
[96]
In general, the flow rate of the separation membrane is inversely proportional to the salt removal rate. Accordingly, as the salt removal rate of the produced water is lowered, it is possible to increase the flow rate of the produced water.
[97]
The flow rate measurement of the produced water may use a water treatment module comprising a plate-type permeation cell, a high-pressure pump, a storage tank, and a cooling device. After the separation membrane is installed in the permeation cell, a preliminary operation is sufficiently performed for about 1 hour using tertiary distilled water to stabilize the evaluation equipment. Then, after confirming that the sodium chloride aqueous solution of 70,000 ppm or more was stabilized by operating the equipment at a flow rate of 400 psi to 1,200 psi and 4 L/min for 1 hour, the amount of water transmitted at 25 ° C. for 10 minutes was measured and the permeation flow rate (flux) ) can be calculated and measured. Specifically, the salt removal rate (%) and the permeation flow rate (flux) may be measured under pH 7 to pH 8 conditions.
[98]
In one embodiment of the present specification, the separation membrane is a reverse osmosis membrane.
[99]
The separation membrane may be a micro filtration membrane, an ultrafiltration membrane, a nano filtration membrane, a reverse osmosis membrane, etc., and preferably a nano filtration membrane (Nano Filtration) or a reverse osmosis membrane (Reverse Osmosis). .
[100]
Other configurations and manufacturing methods of the separation membrane are not particularly limited, and general means known in this field may be employed without limitation.
[101]
The product water obtained by the high salt raw water concentration method according to the present specification may be purified as final product water of drinking water quality through an additional separation process if necessary. The additional separation process is not particularly limited, and a process in the art may be appropriately employed.
Modes for carrying out the invention
[102]
Hereinafter, examples will be given to describe the present specification in detail. However, the embodiments according to the present specification may be modified in various other forms, and the scope of the present specification is not to be construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely explain the present specification to those of ordinary skill in the art.
[103]
[104]
Examples and Comparative Examples.
[105]
Raw water (aqueous sodium chloride solution) having a concentration of 70,000 ppm was passed through the separation membrane under conditions of 25° C. and 800 psi, and the salt permeability constant (B-value), salt removal rate, and flow rate were as shown in Table 1 below.
[106]
For the salt removal rate and flow rate, a water treatment module including a plate-type permeation cell, a high-pressure pump, a storage tank, and a cooling device was used. After the separation membrane was installed in the permeation cell, preliminary operation was sufficiently performed for about 1 hour using tertiary distilled water to stabilize the evaluation equipment. Thereafter, after confirming that the sodium chloride aqueous solution having a concentration of 70,000 ppm was stabilized by operating the equipment at a flow rate of 800 psi and 4 L/min for about 1 hour, the amount of water transmitted at 25° C. for 10 minutes was measured to determine the permeation flow rate (flux) was calculated and the salt removal rate (%) was calculated by measuring the salt concentration before and after permeation using a conductivity meter, which is described in Table 1 below.
[107]
The salt transmittance constant (B-value) and salt removal rate were calculated using the following [Equation 1] and [Equation 2].
[108]
[Equation 1]
[109]
N s = B * (C m - C p ),
[110]
In Formula 1, B is the salt transmittance constant (B-value),
[111]
Ns is the amount of salt that has passed through the separation membrane (GFD * ppm), and is the value of F p * C p ,
[112]
C m is the membrane concentration (ppm) on the raw water side,
[113]
C p is the permeate concentration (ppm),
[114]
F p is the Permeate Flux (GFD).
[115]
[Equation 2]
[116]
Salt Removal Rate = 1 - C p /C f
[117]
In the above formula 2,
[118]
C p is the permeate concentration (ppm),
[119]
C f is the feed concentration (ppm).
[120]
F p (product water flow rate) was measured by measuring the volume of the product water passing through the separation membrane for 10 minutes,
[121]
C p (concentration of produced water) was measured by measuring the conductivity of produced water,
[122]
C m (the surface concentration of the separation membrane on the raw water side) was measured through the concentration and recovery rate of the raw water in Equation 3 below.
[123]
[Equation 3]
[124]
C m = k * C f * Rec
[125]
In Equation 3,
[126]
C m is the surface concentration (ppm) of the separation membrane on the raw water side,
[127]
C f is the raw water concentration (ppm),
[128]
k is the experimental constant,
[129]
Rec is the recovery (%).
[130]
The recovery rate is the ratio of the raw water flow rate and the production water flow rate, and was calculated as the production water flow rate (F p ) / raw water flow rate (F f ).
[131]
C f (raw water concentration) was determined by measuring the conductivity of the raw water.
[132]
The conductivity was measured using a conductivity meter.
[133]
[Table 1]
Salt Removal Rate (%) Flow (GPD) Salt transmittance constant (B-value) (GFD) Product flow (GFD) Production water concentration (ppm)
Example 1 20 10,000 75 20 57,000
Example 2 20 20,000 150 40 60,000
Example 3 50 10,000 22 17 41,000
Example 4 50 20,000 43 33 43,000
Example 5 80 10,000 5.6 11 24,000
Example 6 80 20,000 11 22 25,000
comparative example 99.85 9,000 0.031 0.68 3,000
[134]
[135]
The salt removal rate and flow rate in Table 1 means the performance under standard conditions (800 psi, 25 °C, 32,000 ppm NaCl, 15% recovery, pH 7-8) of the membrane area 400 ft 2 reverse osmosis module.
[136]
The production water flow rate and production water concentration in Table 1 refer to the measured values ​​of the production water passing through each reverse osmosis membrane under the evaluation conditions (NaCl 70,000 ppm, 800 psi, 25°C).
[137]
In Table 1, Example is a case in which high salt raw water is purified using a semi-permeable membrane having high salt permeability, and Comparative Example is a case in which high salt raw water is purified using a semi-permeable membrane having a general low salt transmittance.
[138]
As can be seen in Table 1, in the evaluation results corresponding to Examples, a high production water flow rate can be obtained when high salt raw water is purified under normal reverse osmosis operation conditions, and the produced water collected at this time is additionally reverse osmosis process Through this, it can be purified into final product water of drinking water quality.
[139]
On the other hand, in the case of Comparative Example, it was confirmed that when high-salt raw water was purified under normal reverse osmosis operation conditions, a very low flow rate of produced water was obtained.
[140]
Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and it is possible to carry out various modifications within the scope of the claims and the detailed description of the invention, and this also falls within the scope of the invention. .

WE CLAIMS

High-salt raw water concentration method to obtain product water satisfying the following formula 1 by passing raw water having a concentration of 70,000 ppm or more through a separation membrane at a temperature of 40° C. or less and a pressure of 1,200 psi or less: [Equation 1] N s = B * (C m - C p ), in Equation 1, B is the salt permeability constant (B-value), 3 GFD≤B≤150 GFD, N s is the amount of salt that has passed through the separation membrane (GFD * ppm), F p * This is the value of C p , C m is the membrane concentration (ppm) on the raw water side, and C p is the permeate concentration (ppm). F p is the production water flow rate (Permeate Flux), 5 GFD≤Fp≤100 GFD.
[Claim 2]
The method according to claim 1, wherein the osmotic pressure of the produced water is 15% to 90% of the raw water osmotic pressure.
[Claim 3]
The method according to claim 1, wherein the concentration of the raw water is 70,000 ppm or more and 200,000 ppm or less.
[Claim 4]
The method according to claim 1, wherein the pressure is 400 psi or more and 1,200 psi or less.
[Claim 5]
The method according to claim 1, wherein the salt removal rate of the produced water satisfies the following formula 2, and is 10% or more and 85% or less. [Formula 2] Salt removal rate = (1- C p /C f ) * 100 C p is the permeate concentration (ppm), and C f is the feed concentration (ppm).
[Claim 6]
The method according to claim 1, wherein the flow rate (F p ) per area of ​​the produced water is 5 GFD or more and 100 GFD or less.
[Claim 7]
The method according to claim 1, wherein the separation membrane is a reverse osmosis membrane.