WO2013066662A1

WO2013066662A1 - System and process for treatment of solution

Info

Publication number: WO2013066662A1
Application number: PCT/US2012/061423
Authority: WO
Inventors: Yiwen Sun; Chunjie Liu; Rihua Xiong; Yu Dong; Jiyang Xia; Wei Cai
Original assignee: General Electric Company
Priority date: 2011-10-31
Filing date: 2012-10-23
Publication date: 2013-05-10
Also published as: CN103086533A

Abstract

A treatment process and a treatment system are provided for treating an aqueous saline solution. The treatment process comprises contacting an aqueous saline solution with an effective amount of a miscible organic solvent to precipitate dissolved salts and produce a mixture of precipitated solid salts and a liquid and then removing the precipitated solid salts from the liquid. The treatment process further comprises cooling the liquid to produce an organic phase comprising the miscible organic solvent and an aqueous phase comprising the miscible organic solvent and the dissolved salts and then removing the organic phase from the aqueous phase. The treatment process further comprises introducing the aqueous phase into a membrane device to remove the miscible organic solvent and the dissolved salts from the aqueous phase.

Description

SYSTEM AND PROCESS FOR TREATMENT OF SOLUTION

BACKGROUND

[0001] This invention relates generally to systems and processes for treatments of solutions. More particularly, the invention relates to systems and processes for treatment of aqueous saline solutions using a miscible organic solvent.

[0002] In industrial processes, large amounts of solutions, such as saline solutions are produced. Generally, such aqueous saline solutions are not suitable for direct consumption in domestic or industrial applications. In view of the limited eligible water sources and protection of environment, some treatment processes, such as de-ionization and desaltification for treatment of wastewater, seawater or brackish water, become options to produce eligible water.

[0003] In current applications, various treatment processes, such as distillation and vaporization are employed for treatments of solutions. However, such processes can suffer from low efficiency and/or high-energy consumption, for example, for directly treating solutions of high salinity, such as water used in hydrofracturing, which may prohibit them from being widely implemented.

[0004] Therefore, there is a need for new and improved systems and methods for treatment of aqueous saline solutions.

BRIEF DESCRIPTION

[0005] A treatment process is provided in accordance with one embodiment of the invention. The treatment process comprises contacting an aqueous saline solution with an effective amount of a miscible organic solvent to precipitate dissolved salts and produce a mixture of precipitated solid salts and a liquid and then removing the precipitated solid salts from the liquid. The treatment process further comprises cooling the liquid to produce an organic phase comprising the miscible organic solvent and an aqueous phase comprising the miscible organic solvent and the dissolved salts and then removing the organic phase from the aqueous phase. The treatment process further comprises introducing the aqueous phase into a membrane device to remove the miscible organic solvent and the dissolved salts from the aqueous phase.

[0006] In another aspect, the invention relates to a treatment process. The treatment process comprises introducing a raw solution into a steam generator or an evaporator to evaporate the raw solution and discharge an aqueous saline solution. The treatment process further comprises contacting the aqueous saline solution with an effective amount of a miscible organic solvent to precipitate dissolved salts and produce a mixture of precipitated solid salts and a liquid and then removing the precipitated solid salts from the liquid. The treatment process further comprises cooling the liquid to produce an organic phase comprising the miscible organic solvent and an aqueous phase comprising the miscible organic solvent and the dissolved salts and then removing the organic phase from the aqueous phase. The treatment process further comprises reintroducing the aqueous phase into the steam generator or the evaporator to evaporate the aqueous phase.

[0007] In another aspect, the invention relates to a water treatment system.

The treatment system comprises a precipitation unit configured to contact an aqueous saline solution with an effective amount of a miscible organic solvent to precipitate dissolved salts and produce a mixture of precipitated solid salts and a liquid. The treatment system further comprises a recovery unit in fluid communication with the precipitation unit. The recovery unit is configured to separate the liquid into an organic phase comprising the miscible organic solvent and an aqueous phase comprising the miscible organic solvent and the dissolved salts. The treatment system further comprises a cooling apparatus in fluid communication between the precipitation unit and the recovery unit. The cooling apparatus is configured to cool the liquid from the precipitation unit. The treatment system further comprises a purification unit comprising a membrane device in fluid communication with the recovery unit. The membrane device is configured to remove the miscible organic solvent and the dissolved salts from the aqueous phase.

BRIEF DESCRIPTION OF THE DRAWINGS [0008] The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the subsequent detailed description when taken in conjunction with the accompanying drawings in which:

[0009] FIG. 1 is a schematic diagram of a treatment system for treating an aqueous saline solution in accordance with one embodiment of the invention; and

[0010] FIG. 2 is a schematic flow chart of a treatment process for treating the aqueous saline solution in accordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Embodiments of the present disclosure are described herein with reference to the accompanying drawings. In the subsequent description, well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail. As used herein, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise.

[0012] FIG. 1 is a schematic diagram of a treatment system 10 for treating an aqueous saline solution 17. The aqueous saline solution 17 may be any saline solution. In one example, the aqueous saline solution 17 is discharged from a steam generator 25 or an evaporator 25. In another example, the aqueous saline solution 17 is a waste stream from a Steam Assisted Gravity Drainage (SAGD) process.

[0013] Treatment system 10 is configured to precipitate dissolved salts in the aqueous saline solution 17 using an effective amount of miscible organic solvent to reduce the concentration of the dissolved salts. After the evaporation process, the temperature of the aqueous saline solution 17 is relatively high, ranging from about 80°C to about 200°C. The miscible organic solvent is miscible with water at a higher temperature and separated from water at a lower temperature. The miscible organic solvent may be selected based on different applications.

[0014] In one example, the miscible organic solvent may be an alcohol, such as cyclohexanol, 3-methyl-l-butanol, 3-pentanol, 1-hexanol, 1-pentanol, 2-octanol, 2- ethyl hexanol, cyclopentanol. The alcohol is miscible with water at a higher temperature such as about 85 °C and separated from water at a lower temperature such as about 20°C. In another example, the miscible organic solvent may be a ketone, such as methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK). The ketone is miscible with water at a higher temperature such as about 70 °C and separated from water at a lower temperature such as about 20°C. In another example, the miscible organic solvent may be any combination of the alcohol and the ketone.

[0015] Additionally, non- limiting examples of the dissolved salts in the aqueous saline solution 17 include salts selected from the group consisting of halides of sodium, calcium, barium, strontium, and radium, bicarbonates of sodium, potassium, magnesium, calcium, barium, strontium, and radium, silicates of sodium, potassium, magnesium, and radium, selenites, selenates, selenides of sodium, potassium, magnesium, calcium, barium, strontium, and radium, selenide salts selected from the group consisting of phosphorous sub-selenide, phosphorous monoselenide, phosphorous tri-selenide, and phosphorous penta-selenide, selenium halide salts selected from the group consisting of selenium mono-chloride, selenium tetra-chloride, selenium mono-bromide, and selenium tetra-bromide, phosphates of sodium, potassium, magnesium, calcium, barium, strontium, and radium, boron salts of sodium, potassium, magnesium, calcium, barium, strontium, and radium, sulfate salts of sodium, potassium and radium, carbonate salts of sodium, potassium and magnesium, and combinations thereof.

[0016] As illustrated in FIG. 1, the treatment system 10 includes a precipitation unit 11, a recovery unit 13, a cooling apparatus 27 and a purification unit 14. The precipitation unit 11 includes an organic solvent source 15, a precipitation device 16 in fluid communication with the organic solvent source 15 and a solid- liquid separation unit 12 in fluid communication with the precipitation device 16 and the cooling apparatus 27. The organic solvent source 15 is configured to provide the miscible organic solvent into the precipitation device 16. The precipitation device 16 may comprise a vessel and is configured to accommodate the miscible organic solvent and the aqueous saline solution 17 for the precipitation of precipitated solid salts 18. The aqueous saline solution 17 and the miscible organic solvent may be mixed with each other within the precipitation device 16, so that most of the dissolved salts in the aqueous saline solution 17 precipitate to form a mixture of precipitated solid salts 18 and a liquid 19.

[0017] The solid-liquid separation unit 12 is configured to receive and separate the precipitated solid salts 18 and the liquid 19. Non-limiting examples of the solid-liquid separation unit 12 include hydrocyclones, centrifuges, filter presses, cartridge filters, vacuum filtration devices, and microfiltration devices. The solid- liquid separation unit 12 may include a single device, or multiple devices.

[0018] In some applications, the solid-liquid separation unit 12 may comprise one or more hydrocyclones serially connected to each other. When the mixture of the precipitated solid salts 18 and the liquid 19 from the precipitation unit 11 is introduced into the solid-liquid separation unit 12, the precipitated solid salts 18 may be removed from the liquid 19.

[0019] For the arrangement illustrated in FIG. 1, the cooling apparatus 27 is in fluid communication between the precipitation unit 11 and the recovery unit 13 and configured to cool the liquid 19 from the precipitation unit 1 1. The recovery unit 13 receives the liquid 19 cooled from the cooling apparatus 27. The recovery unit 13 is configured to separate of the liquid 19, for example, to separate a liquid with different phases. In some applications, the liquid 19 is separated into an organic phase 21 comprising the miscible organic solvent and an aqueous phase 20 comprising the miscible organic solvent and the dissolved salts. In some examples, the recovery unit 13 may comprise a vessel, in which the separation of the liquid 19 occurs. In some applications, the recovery unit 13 communicates fluidly with the precipitation unit 11 to reintroduce the miscible organic solvent (the organic phase 21) recovered therefrom into the precipitation unit 11. The recovered miscible organic solvent may be reused.

[0020] After the solid-liquid separation in the precipitation unit 11 , most of the dissolved salts in the aqueous saline solution 17 are removed therefrom. A certain amount of residual dissolved salts may still remain in the liquid 19. After the separation in the recovery unit 13, most of the miscible organic solvent is removed from the liquid 19. A certain amount of residual miscible organic solvent may still remain in the aqueous phase 20 and the residual dissolved salts remain in the aqueous phase 20. Accordingly, the aqueous phase 20 from the recovery unit 13 may be introduced into the purification unit 14 for the separation of the miscible organic solvent and the dissolved salts from the aqueous phase 20.

[0021] In the illustrated example, the purification unit 14 comprises a removal device. The removal device may comprise any devices suitable for the separation of the residual miscible organic solvent and the residual dissolved salts from the aqueous phase 20. In some examples, the removal device may comprise a membrane device to remove the residual miscible organic solvent and the residual dissolved salts. The membrane device comprises a reverse osmosis (RO) membrane or a nano-filtration (NF) membrane.

[0022] Thus, a fluid 22 comprising the residual miscible organic solvent and the residual dissolved salts may be removed from the aqueous phase 20, and a product liquid 24 may be produced. In some applications, the purification unit 14 communicates fluidly with the precipitation unit 11 to reintroduce the miscible organic solvent (the fluid 22) recovered therefrom into the precipitation unit 11. The miscible organic solvent (the fluid 22) may be reused.

[0023] In some embodiments, a raw solution 23 is introduced into the steam generator or evaporator 25 to be evaporated and the aqueous saline solution 17 is discharged therefrom. After the separation in the recovery unit 13, the aqueous phase 20 may be reintroduced into the steam generator or evaporator 25 to be evaporated.

[0024] It should be noted that the arrangement shown in FIG. 1 is merely illustrative. For the illustrated embodiment, the precipitation device 16 and the solid- liquid separation unit 12 are provided separately. Alternatively, the precipitation device 16 and the solid- liquid separation unit 12 may be integrated to act as one element for performing the precipitation and the separation.

[0025] FIG. 2 is a schematic flow chart of a treatment process 30. As illustrated in FIGS. 1-2, during the treatment process, in step 31, the aqueous saline solutions 17 are delivered into the precipitation unit 11. The effective amount of the miscible organic solvent from the organic solvent source 15 are also introduced into the precipitation device 16 to mixed with the aqueous saline solution 17. If the miscible organic solvent is less than the effective amount, the dissolved salts are not precipitated. The effective amounts of the miscible organic solvents are different according to concentrations of the dissolved salts, species of the dissolved salts and species of the miscible organic solvent. The aqueous saline solution 17 is contacted with the effective amount of the miscible organic solvent to precipitate the dissolved salts due to their lower solubility in the miscible organic solvent and produce the mixture of the precipitated solid salts 18 and the liquid 19. When a concentration of the dissolved salts is higher than 4 wt%, dissolved salts can be precipitated by the miscible organic solvent at low cost. And a concentration of the miscible organic solvent is lower than 93.75 wt%, so that make sure there is not too much miscible organic solvent in the aqueous saline solutions 17 in the case of the dissolved salts are precipitated. The concentration of miscible organic solvent is a weight percentage of the miscible organic solvent with respect to a total weight of the miscible organic solvent and H₂0.

[0026] In step 32, the precipitated solid salts 18 and the liquid 19 are introduced into the so lid- liquid separation unit 12 for separation. In step 33, after the separation of the precipitated solid salts 18 from the liquid 19, the liquid 19 from the so lid- liquid separation unit 12 is introduced through the cooling apparatuses 27 to be cooled to a lower temperature. In step 34, the liquid 19 is introduced into the recovery unit 13 and the miscible organic solvent (the organic phase 21) is separated from the liquid 19 at the lower temperature within the recovery unit 13 in the form of layers of the organic phase 21 and the aqueous phase 20.

[0027] In some embodiments, subsequently, in step 35, the aqueous phase 20 is introduced into the purification unit 14 for separation of the miscible organic solvent and the dissolved salts from the aqueous phase 20. In some applications, the miscible organic solvent recovered in step 34 and/or step 35 may be reintroduced into the precipitation device 16 to be reused. [0028] In some applications, before step 31, a raw solution 23 is introduced into the steam generator or evaporator 25 to be evaporated and the aqueous saline solution 17 is discharged from the steam generator or evaporator 25 with a higher temperature. After step 34, the aqueous phase 20 is reintroduced into the steam generator or evaporator 25 to be evaporated to produce product water.

[0029] Accordingly, in embodiments of the invention, due to the presence of the miscible organic solvent in the solution, the salt species may be removed with lower cost and higher efficiency. The aqueous saline solution with a high temperature may be mixed directly with the miscible organic solvent without being cooled. Thereby, the treatment process is simplified. In addition, after separating the aqueous phase and the organic phase, the aqueous phase is reintroduced into the steam generator to produce product water via being evaporated, thereby the treatment process and system are simplified.

Example 1

[0030] Cyclohexanol was mixed with a NaCl solution including 6 wt%, 8 wt% or 10 wt% NaCl at 90 °C. The concentration of cyclohexanol was 95 wt% which was a weight percentage of cyclohexanol with respect to a total weight of cyclohexanol and H₂0. Solid NaCl was precipitated from the NaCl solution and separated therefrom to produce a liquid. And the solid NaCl was dried for two hours. When the liquid was cooled to a room temperature, it separated into an organic phase and an aqueous phase. The concentration of NaCl, the weight of NaCl solution , the weight of cyclohexanol, the weight of solid NaCl and the removal percentage of NaCl are listed in table 1 below.

Table 1

[0031] It can be seen from table 1 that most of the salt can be removed even if at a low salt concentration and the salt removal percentage becomes greater with the increase of the salt concentration. More than 81% salt of the salt solution with more than 6 wt% salt concentration was precipitated by cyclohexanol (95 wt%).

Example 2

[0032] This experiment was similar to example 1 but the concentration of cyclohexanol was changed. The concentration of cyclohexanol is represented as weight percentage of cyclohexanol with respect to a total weight of cyclohexanol and H₂0, not including weight of NaCl. The concentration of NaCl, the weight of NaCl solution, the weight of cyclohexanol, the concentration of cyclohexanol and the removal percentage of NaCl are listed in table 2 below.

Table 2

15.395 190.041 93.20 wt% 78.37%

14.307 190.22 93.66 wt% 86.42%

14.31 190.232 93.66 wt% 77.40%

11.127 191.144 95.02 wt% 89.29%

11.131 191.554 95.03 wt% 88.54%

[0033] It can be seen from table 2 that the concentration of NaCl and the concentration of cyclohexanol affect the salt removal performance. When the concentration of NaCl is lower than 6 wt%, the concentration of cyclohexanol is higher than 93.4 wt%. For 6 wt% NaCl solution, the effective concentration of cyclohexanol is high than 93.4 wt%. For 8 wt% NaCl solution, the effective concentration of cyclohexanol is high than 91.75 wt%. For 10 wt% NaCl solution, the effective concentration of cyclohexanol is high than 91.28 wt%. When the concentration of cyclohexanol was higher than 94.5 wt%, more than 60wt% salt was precipitated from the 6 wt% NaCl solution and when the concentration of cyclohexanol was higher than 93.2 wt%, more than 60wt% salt was precipitated from 8 wt% and 10 wt% NaCl solutoins. For NaCl solution with lower concentration of NaCl, higher concentration of the cyclohexanol was needed to remove the same percentage of NaCl.

Example 3

[0034] A flat sheet RO membrane or NF membrane was used in the membrane device. A simulation aqueous phase was prepared by dissolving 30g of NaCl and 15g of cyclohexanol in 29L deionized water at room temperature. The simulation aqueous phase was pumped through the RO or NF membrane at a flow rate of 2L/min to produce a RO permeate solution or a NF permeate solution. The pressure drop from the feed side to the permeate side of the RO membrane was 200psi or the NF membrane was 70psi. The conductivity and COD of the simulation aqueous phase, the RO permeate solution and the NF permeate solution are listed in table 3 below.

Table 3

NF permeate solution 1076 804

[0035] The conductivity and COD indicated the concentration of NaCl and cyclohexanol respectively. It can be seen from table 3 that the conductivities and CODs of the RO permeate solution and the NF permeate solution are much lower than these of the simulation aqueous phase, thereby most of NaCl and cyclohexanol in the simulation aqueous phase are removed. The conductivity of the RO permeate solution is 1.1% of that of the simulation aqueous phase, so the RO membrane rejected 98.9% NaCl and the COD of the RO permeate solution is 0.5% of that of the simulation aqueous phase, so the RO membrane rejected 99.5% cyclohexanol. Similarly, the NF membrane rejected 50% NaCl as well as 54% cyclohexanol in the simulation aqueous.

[0036] While the disclosure has been illustrated and described in typical embodiments, it is not intended to be limited to the details shown, since various modifications and substitutions can be made without departing in any way from the spirit of the present disclosure. As such, further modifications and equivalents of the disclosure herein disclosed may occur to persons skilled in the art using no more than routine experimentation, and all such modifications and equivalents are believed to be through the spirit and scope of the disclosure as defined by the subsequent claims.

Claims

WHAT IS CLAIMED IS:

1. A treatment process, comprising:

contacting an aqueous saline solution with an effective amount of a miscible organic solvent to precipitate dissolved salts and produce a mixture of precipitated solid salts and a liquid;

removing the precipitated solid salts from the liquid;

cooling the liquid to produce an organic phase comprising the miscible organic solvent and an aqueous phase comprising the miscible organic solvent and the dissolved salts;

removing the organic phase from the aqueous phase; and

introducing the aqueous phase into a membrane device to remove the miscible organic solvent and the dissolved salts from the aqueous phase.

2. The treatment process of claim 1, wherein the miscible organic solvent comprises an alcohol or a ketone.

3. The treatment process of claim 2, wherein the miscible organic solvent comprises cyclohexanol, 3 -methyl- 1-butanol, 3-pentanol, 1-hexanol, 1-pentanol, 2- octanol, 2-ethyl hexanol, cyclopentanol, methyl ethyl ketone, methyl isobutyl ketone, or any combination thereof.

4. The treatment process of claim 1, wherein the miscible organic solvent is cyclohexanol.

5. The treatment process of claim 1, wherein the dissolved salt is NaCl and the miscible organic solvent is cyclohexanol, when a concentration of NaCl is lower than 6 wt%, a concentration of cyclohexanol is higher than 93.4 wt%.

6. The treatment process of claim 1, wherein a concentration of the dissolved salts is higher than 4 wt% and a concentration of the miscible organic solvent is lower than 93.75 wt%.

7. The treatment process of claim 1, further comprising introducing a raw solution into a steam generator or an evaporator to evaporate the raw solution and discharge the aqueous saline solution before the step of contacting.

8. The treatment process of claim 1, wherein the membrane device comprises a reverse osmosis membrane or a nano-filtration membrane.

9. A treatment process, comprising:

introducing a raw solution into a steam generator or an evaporator to evaporate the raw solution and discharge an aqueous saline solution;

contacting the aqueous saline solution with an effective amount of a miscible organic solvent to precipitate dissolved salts and produce a mixture of precipitated solid salts and a liquid;

removing the precipitated solid salts from the liquid;

removing the organic phase from the aqueous phase; and

reintroducing the aqueous phase into the steam generator or the evaporator to evaporate the aqueous phase.

10. The treatment process of claim 9, wherein the miscible organic solvent comprises an alcohol or a ketone.

11. The treatment process of claim 10, wherein the miscible organic solvent comprises cyclohexanol, 3 -methyl- 1-butanol, 3-pentanol, 1-hexanol, 1- pentanol, 2-octanol, 2-ethyl hexanol, cyclopentanol, methyl ethyl ketone, methyl isobutyl ketone, or any combination thereof.

12. The treatment process of claim 9, wherein the miscible organic solvent is cyclohexanol.

13. The treatment process of claim 9, wherein the dissolved salts are NaCl and the miscible organic solvent is cyclohexanol, when a concentration of NaCl is lower than 6 wt%, a concentration of cyclohexanol is higher than 93.4 wt%.

14. The treatment process of claim 9, wherein a concentration of the dissolved salts is higher than 4 wt% and a concentration of the miscible organic solvent is lower than 93.75 wt%.

15. A treatment system, comprising:

a precipitation unit configured to contact an aqueous saline solution with an effective amount of a miscible organic solvent to precipitate dissolved salts and produce a mixture of precipitated solid salts and a liquid;

a recovery unit in fluid communication with the precipitation unit and configured to separate the liquid into an organic phase comprising the miscible organic solvent and an aqueous phase comprising the miscible organic solvent and the dissolved salts;

a cooling apparatus in fluid communication between the precipitation unit and the recovery unit and configured to cool the liquid from the precipitation unit; and a purification unit comprising a membrane device in fluid communication with the recovery unit and configured to remove the miscible organic solvent and the dissolved salts from the aqueous phase.

16. The treatment system of claim 15, wherein the precipitation unit comprises an organic solvent source, a precipitation device in fluid communication with the organic solvent source and a solid-liquid separation unit in fluid communication with the precipitation device and the cooling apparatus, and wherein the organic solvent source is configured to provide the miscible organic solvent into the precipitation device, the precipitation device is configured to accommodate the miscible organic solvent and the aqueous saline solution for the precipitation of the precipitated solid salts, and the solid-liquid separation unit is configured to separate the precipitated solid salts and the liquid.

17. The treatment system of claim 15, wherein the miscible organic solvent comprises an alcohol or a ketone.

18. The treatment system of claim 17, wherein the miscible organic solvent comprises cyclohexanol, 3 -methyl- 1-butanol, 3-pentanol, 1-hexanol, 1- pentanol, 2-octanol, 2-ethyl hexanol, cyclopentanol, methyl ethyl ketone, methyl isobutyl ketone, or any combination thereof.

19. The treatment system of claim 15, further comprising a steam generator or an evaporator disposed upstream from and in fluid communication with the precipitation unit, and configured to evaporate a raw solution and to discharge the aqueous saline solution.

20. The treatment system of claim 15, wherein the one or more membrane devices comprises a reverse osmosis membrane or a nano-filtration membrane.

21. The treatment system of claim 15, wherein the recovery unit and the purification unit respectively communicate fluidly with the precipitation unit to reintroduce the miscible organic solvent recovered therefrom into the precipitation unit.