Fracturing flow-back fluid treatment process

Abstract

The invention provides a fracturing flow-back fluid treatment process, and belongs to the field of oilfield chemical engineering. The technology comprises the following steps: carrying out coagulation treatment on the fracturing flow-back fluid, carrying out oxidation treatment on the coagulation treatment fluid by using a hydroxylamine hydrochloride reinforced ferrate technology, and sequentially carrying out microfiltration treatment and nanofiltration treatment on the oxidation treatment fluid to obtain purified water. The hydroxylamine enhanced ferrate oxidation technology and the microfiltration-nanofiltration technology are combined, the concentration of pollutants can be reduced, so that pollution to a membrane is reduced, the load of nanofiltration can be reduced through preliminary microfiltration, the fracturing flow-back fluid can be effectively treated through the combined technology, COD, TOC, UV254 and TDS in the fracturing flow-back fluid can be remarkably reduced, and meanwhile membrane pollution is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the oil field chemical industry, in particular to a fracturing flowback fluid treatment process. BACKGROUND

[0002] In order to prevent the fracturing flowback fluid from causing serious pollution to groundwater and surface water, the fracturing flowback fluid needs to be treated before being discharged.

[0003] At present, the treatment process of fracturing flowback fluid includes electric flocculation method, Fenton oxidation method, biological treatment method, and full membrane method, etc., however, the known treatment processes of fracturing flowback fluid all have various adverse factors, so it is difficult to significantly improve the treatment quality of fracturing flowback fluid under the premise of reducing cost, for example, significantly reducing the removal rates of COD, TOC, UV 254 and TDS. SUMMARY

[0004] In view of this, the present application provides a fracturing flowback fluid treatment process, which can solve the technical problems in the related art.

[0005] Specifically, the technical scheme includes the following:

[0006] A fracturing flowback fluid treatment process, the fracturing flowback fluid treatment process includes: coagulating the fracturing flowback fluid to obtain a coagulation treatment liquid;

[0007] Using hydroxylamine hydrochloride to intensify the high ferric salt process to oxidize the coagulation treatment liquid to obtain an oxidation treatment liquid;

[0008] Sequentially micro-filtering and nanofiltrating the oxidation treatment liquid to obtain purified water, and completing the treatment of the fracturing flowback fluid.

[0009] In some possible implementation manners, the coagulant used in the coagulation treatment includes at least one of polyaluminum chloride (PAC) and polyacrylamide (PAM).

[0010] In some possible implementation manners, the amount of the polyaluminum chloride (PAC) is 100 mg / L-1000 mg / L.

[0011] The amount of the polyacrylamide (PAM) is 10 mg / L-30 mg / L.

[0012] In some possible implementation manners, the coagulation treatment of the fracturing flowback fluid to obtain the coagulation treatment liquid includes:

[0013] Polyaluminum chloride (PAC) is added to the fracturing flowback fluid, stirred uniformly at a speed of 600 r / min-1000 r / min, then polyacrylamide (PAM) is added to the solution, stirred uniformly at a speed of 100 r / min-300 r / min, and the coagulation treatment liquid is obtained after standing.

[0014] In some possible implementation manners, the process of using hydroxylamine hydrochloride to strengthen the high ferric salt process to perform oxidation treatment on the coagulation treatment liquid to obtain an oxidation treatment liquid comprises: filtering the coagulation treatment liquid, then adding hydroxylamine hydrochloride thereto, adjusting the pH of the solution to neutral, and then adding high ferric salt dissolved in a phosphoric acid-boric acid buffer solution to achieve the oxidation treatment on the coagulation treatment liquid.

[0015] In some possible implementation manners, the amount of the high ferric salt is 1 g / L-5 g / L.

[0016] The amount of the hydroxylamine hydrochloride is 10 mg / L-20 mg / L.

[0017] In some possible implementation manners, the ratio of the amount of the high ferric salt to the amount of the hydroxylamine hydrochloride is 100:0.2-0.8.

[0018] In some possible implementation manners, when the process of using hydroxylamine hydrochloride to strengthen the high ferric salt process is used to perform oxidation treatment on the coagulation treatment liquid, the reaction temperature is 20℃-30℃, and the reaction time is 30 min-100 min.

[0019] In some possible implementation manners, the microfiltration treatment adopts a microfiltration membrane, and the pore size of the microfiltration membrane is 0.1 micrometer-10 micrometers.

[0020] In some possible implementation manners, the nanofiltration treatment adopts a nanofiltration membrane, and the pore size of the nanofiltration membrane is 0.1 nanometer-10 nanometers.

[0021] The technical scheme provided by the embodiment of the application has at least the following beneficial effects:

[0022] The fracturing flowback fluid treatment process provided by the embodiment of the present application firstly performs coagulation treatment on the fracturing flowback fluid to remove the obviously existing suspended solids and reduce the subsequent treatment pressure. Then, the hydroxylamine hydrochloride reinforced high ferrate process is used to perform oxidation treatment on the coagulation treatment liquid, which can not only oxidize part of the organic matters in the fracturing flowback fluid, but also degrade the refractory macromolecular organic matters in the fracturing flowback fluid into easily degradable small molecular organic matters. The oxidation products of the organic matters and the small molecular organic matters can smoothly pass through the microfiltration membrane and be intercepted by the nanofiltration membrane in the subsequent microfiltration and nanofiltration treatment process, so that the membrane pollution of the microfiltration membrane and the nanofiltration membrane can be reduced under the premise of realizing effective purification. It can be seen that, in view of the problems of high suspended solids, high COD, high TDS and high TOC of the fracturing flowback fluid, the hydroxylamine reinforced high ferrate oxidation technology is combined with the microfiltration-nanofiltration technology. On the one hand, the oxidation treatment can reduce the pollutant concentration and thus reduce the membrane pollution; on the other hand, the microfiltration preliminary filtration can reduce the nanofiltration load. The combined process can effectively treat the fracturing flowback fluid, significantly reduce the COD, TOC, UV 254 and TDS in the fracturing flowback fluid, and effectively reduce the membrane pollution. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0024] Figure 1 The relationship curve between the PAC dosage and TOC and TNU provided by the embodiment of the present application;

[0025] Figure 2 The relationship curve between the PAM dosage and TOC and TNU provided by the embodiment of the present application;

[0026] Figure 3 The COD removal rate distribution diagram of the fracturing flowback fluid treated by the hydroxylamine reinforced high ferrate oxidation under different HA contents provided by the embodiment of the present application;

[0027] Figure 4 The TOC removal rate distribution diagram of the fracturing flowback fluid treated by the hydroxylamine reinforced high ferrate oxidation under different HA contents provided by the embodiment of the present application;

[0028] Figure 5 The UV 254 removal rate distribution diagram of the fracturing flowback fluid treated by the hydroxylamine reinforced high ferrate oxidation under different HA contents provided by the embodiment of the present application;

[0029] Figure 6A GC-MS spectrum of the original water sample of the fracturing flowback fluid provided by the embodiment of the present application;

[0030] Figure 7 A GC-MS spectrum of the water sample obtained after the fracturing flowback fluid is treated by coagulation and oxidation;

[0031] Figure 8 A content distribution graph of COD and BOD5 in different water samples provided by the embodiment of the present application;

[0032] Figure 9 3D-EEM spectra of some different water samples provided by the embodiment of the present application;

[0033] Figure 10 3D-EEM spectra of some different water samples provided by the embodiment of the present application;

[0034] Figure 11 A membrane flux distribution graph of a membrane after being passed through by different water samples provided by the embodiment of the present application;

[0035] Figure 12 A membrane flux distribution graph of a membrane after being passed through by different water samples provided by the embodiment of the present application;

[0036] Figure 13 An infrared ATR-FITR graph of a microfiltration membrane after being passed through by different water samples provided by the embodiment of the present application;

[0037] Figure 14 An infrared ATR-FITR graph of a nanofiltration membrane after being passed through by different water samples provided by the embodiment of the present application;

[0038] Figure 15 An atomic force microscope image of a microfiltration membrane after being passed through by different water samples provided by the embodiment of the present application;

[0039] Figure 16 An atomic force microscope image of a nanofiltration membrane after being passed through by different water samples provided by the embodiment of the present application.

[0040] The specific embodiments of the present application have been shown by the above-mentioned drawings, and will be described in more detail hereinafter. These drawings and textual descriptions are not intended to limit the scope of the concept of the present application by any means, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0041] Clearly, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0042] At present, the treatment process of fracturing flowback fluid includes: electrocoagulation method, Fenton oxidation method, biological treatment method, full membrane method and the like. However, the known treatment processes of fracturing flowback fluid all have various adverse factors, so it is difficult to significantly improve the treatment quality of fracturing flowback fluid under the premise of reducing cost, for example, significantly reducing the removal rates of COD, TOC, UV 254 and TDS.

[0043] In view of the technical problems of the related art, the embodiments of the present application provide a fracturing flowback fluid treatment process, which comprises the following steps:

[0044] Step 1, coagulating the fracturing flowback fluid to obtain a coagulation treatment liquid.

[0045] Step 2, using hydroxylamine hydrochloride to intensify the high ferrate process to oxidize the coagulation treatment liquid to obtain an oxidation treatment liquid.

[0046] Step 3, sequentially performing microfiltration treatment and nanofiltration treatment on the oxidation treatment liquid to obtain purified water, and completing the treatment of the fracturing flowback fluid.

[0047] Ferrate is a hexavalent iron oxyacid salt, and the effective component ferrate has strong oxidizing property, so that it is a solid oxidant with strong oxidizing and coagulating functions. Common ferrates include sodium ferrate (Na2FeO4), potassium ferrate (K2FeO4) and the like. Taking potassium ferrate as an example, its electrode potential value is 2.20V, and it has strong oxidizing capacity. Its oxidation reaction follows a single electron (1e) or double electron (2e) transfer mechanism, respectively producing unstable Fe(V) and Fe(IV). On this basis, the embodiments of the present application intensify ferrate by using hydroxylamine hydrochloride (HONH2HCl), and promote the generation of Fe(IV) and Fe(V) by using hydroxylamine (HA). The reaction rate constant of Fe(IV) and Fe(V) in oxidizing organic matter is several orders of magnitude higher than that of Fe(VI), and it can also deeply degrade organic pollutants containing ethers, fats, alcohols and phenols. It can be seen that the hydroxylamine-intensified ferrate oxidation treatment technology can not only oxidize and degrade general organic matter which is difficult to degrade by oxidation, but also avoid the generation of toxic by-products containing chlorine when the current free radical oxidation process is used to treat fracturing wastewater.

[0048] Membrane filtration technology has the functions of separation, purification and concentration, and has the advantages of energy saving, high efficiency, no phase change and simple equipment operation, and is widely used in the field of water treatment. The hydroxylamine enhanced ferric oxide oxidation treatment technology is coupled with the microfiltration (MF)-nanofiltration (NF) process to further treat the wastewater, and in the case of ensuring the effluent, the fracturing flowback fluid after the ferric oxide oxidation significantly improves the membrane flux and reduces the pollution to the membrane.

[0049] The fracturing flowback fluid treatment process provided by the embodiments of the present application first coagulates the fracturing flowback fluid to remove the obvious suspended solids and reduce the subsequent treatment pressure. Then, the hydroxylamine hydrochloride enhanced ferric oxide process is used to oxidize the coagulation treatment liquid, which not only can oxidize part of the organic matter in the fracturing flowback fluid, but also can degrade the refractory macromolecular organic matter in the fracturing flowback fluid into easily degradable small molecular organic matter. The oxidation products of the organic matter and the small molecular organic matter can smoothly pass through the microfiltration membrane and be intercepted by the nanofiltration membrane in the subsequent microfiltration and nanofiltration treatment process, so that the membrane flux is improved and the pollution to the membrane is reduced. It can be seen that the embodiments of the present application are aimed at the problems of high suspended solids, high COD, high TDS and high TOC in the fracturing flowback fluid, and the hydroxylamine enhanced ferric oxide oxidation technology is combined with the microfiltration-nanofiltration technology. On the one hand, the oxidation treatment can reduce the concentration of pollutants and thus reduce the pollution to the membrane. On the other hand, the microfiltration preliminary filtration can reduce the nanofiltration load. The combined process can effectively treat the fracturing flowback fluid, significantly reduce the COD, TOC, UV 254 and TDS in the fracturing flowback fluid, and effectively reduce the membrane pollution.

[0050] In some examples, the coagulant used in the coagulation treatment in step 1 includes at least one of polyaluminum chloride (PAC) and polyacrylamide (PAM).

[0051] The coagulation treatment of the fracturing flowback fluid by using the coagulant PAC and the coagulant aid PAM can remove the high suspended solids SS and part of the organic matter in the fracturing flowback fluid. It can be seen that the coagulation effect of PAC and / or PAM can effectively reduce the turbidity of the fracturing flowback fluid.

[0052] For example, the amount of polyaluminum chloride (PAC) added to the fracturing flowback fluid is 100 mg / L to 1000 mg / L, which includes but is not limited to 200 mg / L, 300 mg / L, 400 mg / L, 500 mg / L, 600 mg / L, 700 mg / L, 800 mg / L, 900 mg / L, 1000 mg / L, etc. The amount of polyacrylamide (PAM) is 10 mg / L to 30 mg / L, which includes but is not limited to 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, etc.

[0053] In some examples, the coagulant includes both polyaluminum chloride PAC and polyacrylamide PAM, wherein the polyaluminum chloride PAC is used in an amount of 600 mg / L, and the polyacrylamide PAM is used in an amount of 20 mg / L. For this technical solution, the turbidity of the fracturing flowback fluid can be greatly reduced, and the removal rate of TOC is best.

[0054] The application embodiment also verifies the amount of polyaluminum chloride PAC and polyacrylamide PAM in combination with related experiments, and the experimental results are shown in Figure 1 and Figure 2 It can be seen that the optimal amount of PAC is 600 mg / L, and the optimal amount of PAM is 20 mg / L. Under this amount, the turbidity of the fracturing flowback fluid can be greatly reduced, and the removal rate of TOC is best.

[0055] In combination with the above-mentioned coagulation treatment scheme, in some examples, the fracturing flowback fluid is subjected to coagulation treatment to obtain a coagulation treatment liquid, including: adding polyaluminum chloride PAC to the fracturing flowback fluid, stirring uniformly at a speed of 600 r / min-1000 r / min, then adding polyacrylamide PAM to the solution, stirring uniformly at a speed of 100 r / min-300 r / min, and standing to obtain the coagulation treatment liquid. Through the above coagulation treatment steps, efficient coagulation treatment can be achieved.

[0056] For example, the coagulation treatment can further include: adding polyaluminum chloride PAC to the fracturing flowback fluid, the amount of which is 600 mg / L, stirring uniformly at a speed of 800 r / min for 10 minutes, then adding polyacrylamide PAM to the solution, the amount of which is 20 mg / L, stirring uniformly at a speed of 200 r / min for 5 minutes, and standing for 10 minutes to obtain the coagulation treatment liquid.

[0057] In some examples, the coagulation treatment liquid is subjected to oxidation treatment by using hydroxylamine hydrochloride to intensify the high ferric salt process, to obtain an oxidation treatment liquid, including: filtering the coagulation treatment liquid, then adding hydroxylamine hydrochloride thereto, adjusting the pH of the solution to neutral, and then adding high ferric salt dissolved in a phosphoric acid-boric acid buffer solution to achieve oxidation treatment of the coagulation treatment liquid.

[0058] Through the above oxidation treatment steps, the liquid obtained by filtering after coagulation can be subjected to intensified high ferric salt oxidation, effectively removing part of the organic matter in the fracturing flowback fluid and degrading macromolecular organic matter.

[0059] The pH of the solution can be adjusted to neutral by using 0.5 mol / L H2SO4 or 0.5 mol / L HCl.

[0060] Ferrate dissolved in phosphate-boric acid buffer solution can be obtained by adding a certain amount of ferrate powder to phosphate-boric acid buffer solution (5mM Na2HPO4, 1mM Na2B4O7·H2O, ferrate concentration of 3000mg / L, used within 1min).

[0061] In some examples, the dosage of ferrate is 1 g / L to 5 g / L, including but not limited to: 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, etc., and the dosage of hydroxylamine hydrochloride is 10 mg / L to 20 mg / L, including but not limited to: 10 mg / L, 11 mg / L, 12 mg / L, 13 mg / L, 14 mg / L, 15 mg / L, 16 mg / L, 17 mg / L, 18 mg / L, 19 mg / L, 20 mg / L, etc. For example, the dosage of ferrate is 3 g / L, and the dosage of hydroxylamine hydrochloride is 15 mg / L.

[0062] Furthermore, the ratio of ferrate to hydroxylamine hydrochloride is 100:0.2-0.8, including but not limited to: 100:0.2, 100:0.3, 100:0.4, 100:0.5, 100:0.6, 100:0.7, 100:0.8, etc.

[0063] In some examples, when using hydroxylamine hydrochloride-enhanced ferrate process to oxidize coagulated liquid, the reaction temperature is 20℃~30℃ and the reaction time is 30min~100min. For example, it can be reacted at 25℃ for 60min.

[0064] This invention embodiment tested the relationship between the dosage of ferrate and hydroxylamine hydrochloride and the removal rate of organic matter in fracturing flowback fluid. The experimental conditions were set with the dosage of ferrate Fe(VI) at 3 g / L.

[0065] One test investigated the relationship between the dosage of ferrate and hydroxylamine hydrochloride and the COD removal rate in fracturing flowback fluid. The test results are shown below. Figure 3 ,Depend on Figure 3 It can be seen that when ferrate and hydroxylamine hydrochloride (HA) are used in combination, a small amount of HA increases the COD removal rate. The COD removal rate still increases first and then decreases. When the mass ratio of Fe(VI):HA is 100:0.5 (i.e., Fe(VI) is 3 g / L and HA is 15 mg / L), the COD removal rate in the fracturing flowback fluid reaches the highest level of 32.92%.

[0066] Another test investigated the relationship between the dosage of ferrate and hydroxylamine hydrochloride and the TOC removal rate in the fracturing flowback fluid. The test results are shown below. Figure 4 ,Depend on Figure 4It can be seen that when ferrate and hydroxylamine hydrochloride (HA) are used in combination, a small amount of HA increases the TOC removal rate. The TOC removal rate still increases first and then decreases. When the mass ratio of Fe(VI):HA is 100:0.5 (i.e., Fe(VI) is 3 g / L and HA is 15 mg / L), the TOC removal rate in the fracturing flowback fluid reaches the highest level of 33.69%.

[0067] Another test involved measuring the dosage of ferrate and hydroxylamine hydrochloride in relation to UV levels in the fracturing flowback fluid. 254 The relationship between the removal rate and the test results is shown below. Figure 5 ,Depend on Figure 5 It can be seen that when ferrate is used in combination with hydroxylamine hydrochloride (HA), a small amount of HA increases UV radiation. 254 Removal rate, UV 254 The removal rate initially increased and then decreased. At a Fe(VI):HA mass ratio of 100:0.5 (i.e., Fe(VI) = 3 g / L, HA = 15 mg / L), the UV concentration in the fracturing flowback fluid... 254 The removal rate reached its highest level, at 62.51%.

[0068] In summary, for the fracturing flowback fluid treatment process provided in this embodiment of the invention, under the experimental conditions of Fe(VI) dosage of 3 g / L, HA dosage of 15 mg / L, reaction temperature of 25℃, and reaction time of 60 min, the average removal rate of COD and TOC of the fracturing flowback fluid can reach over 30%. 254 The average removal rate can reach about 60%. It is simple to operate and has high removal efficiency, which can reduce the treatment cost of fracturing flowback fluid.

[0069] Based on the aforementioned tests relating the dosage of ferrate and hydroxylamine hydrochloride to the removal rate of organic matter in fracturing flowback fluid, this embodiment of the invention also performs GC-MS analysis on the fracturing flowback fluid sample before and after the oxidation reaction. The GC-MS spectrum of the original fracturing flowback fluid sample is shown in [reference needed]. Figure 6 The distribution of organic matter contained therein can be found in Table 1.

[0070] Table 1

[0071]

[0072]

[0073] The GC-MS spectra of the original fracturing flowback fluid sample, after sequential coagulation treatment and hydroxylamine hydrochloride-enhanced ferrate oxidation treatment, are shown in the figure below. Figure 7 The distribution of organic matter contained therein can be found in Table 2.

[0074] Table 2

[0075]

[0076] As can be seen from the above, the organic species is obviously reduced after the coagulation treatment liquid of the fracturing flowback fluid is subjected to the oxidation treatment, which indicates that the oxidation treatment involved in the embodiment of the application can effectively remove part of the organic matters in the fracturing flowback fluid.

[0077] The embodiment of the application also tests the content of COD and BOD5 in the above-mentioned original water sample of the fracturing flowback fluid (RW) and the water sample after the oxidation treatment of the fracturing flowback fluid (Fe(VI)-HA), and the test results are shown in Table 1. Figure 8 As can be seen from the above, Figure 8 It can be seen that, by using hydroxylamine hydrochloride to strengthen the oxidation of the ferrate on the fracturing flowback fluid, the process can not only oxidize part of the organic matters in the fracturing flowback fluid, but also degrade the difficult biodegradable macromolecular organic matters in the fracturing flowback fluid into the easily biodegradable small molecular organic matters, so that the water sample after the oxidation treatment improves the biodegradability (the B / C ratio is obviously improved).

[0078] In the embodiment of the application, the microfiltration treatment adopts a microfiltration membrane, the pore size of the microfiltration membrane is 0.1 micrometers to 10 micrometers, and one exemplary microfiltration treatment is that the water sample after the coagulation treatment and the oxidation treatment is subjected to the microfiltration treatment through a water system microfiltration membrane with a pore size of 0.45 micrometers under 0.2 MPa, for example, the water system microfiltration membrane can pass the MF membrane (microfiltration membrane) by using the TYLG-19 high-pressure flat membrane experimental equipment of Shandong Bonai Group.

[0079] In the embodiment of the application, the nanofiltration treatment adopts a nanofiltration membrane, the pore size of the nanofiltration membrane is 0.1 nanometer to 10 nanometer. One exemplary nanofiltration treatment is that the water sample after the coagulation treatment, the oxidation treatment and the microfiltration treatment is subjected to the nanofiltration treatment through a nanofiltration membrane under 2 MPa, for example, the nanofiltration membrane can pass the NF membrane (nanofiltration membrane) by using the TYLG-19 high-pressure flat membrane experimental equipment of Shandong Bonai Group.

[0080] The embodiment of the application also provides the following water samples: the above-mentioned original water sample of the fracturing flowback fluid (RW), the water sample after the oxidation treatment of the fracturing flowback fluid (Fe(VI)-HA), the water sample after the microfiltration treatment of the original water sample by the microfiltration membrane (RW-MF), the water sample after the oxidation treatment and the microfiltration treatment of the fracturing flowback fluid by the microfiltration membrane (Fe(VI)-HA-MF), the water sample after the microfiltration-nanofiltration treatment of the original water sample (RW-NF), and the water sample after the oxidation treatment and the microfiltration-nanofiltration treatment of the fracturing flowback fluid (Fe(VI)-HA-NF), and the 3D-EEM maps of these water samples are tested, and the related maps are shown in Table 2. Figure 9 and Figure 10 and the organic matter removal data of each area of the 3D-EEM map can be seen from Table 3.

[0081] Table 3

[0082]

[0083] VI and V region contain many organic substances, such as phenolic compounds, polycyclic aromatic hydrocarbons (PAHs) and hydrophobic organic acids many organic substances. The original water sample (RW), the water sample after oxidation (Fe(VI)-HA), and the water sample after two kinds of membranes are analyzed by 3D-EEM, and the results show that the removal effect of the water sample in the IV region and the V region after oxidation is obviously higher than that of the water sample directly after membrane, which shows that the water quality of the water after membrane after oxidation is better than that of the water directly after membrane. It can be seen that the content of phenolic compounds, polycyclic aromatic hydrocarbons and organic matter is effectively reduced by the strong oxidation performance of ferrate, and the water quality of the water after MF membrane and NF membrane after oxidation is better, and the COD, TOC, UV 254 and TDS are effectively removed.

[0084] The present application also detects the water quality indicators in each of the above water samples, and analyzes the content of TOC and COD, and the test results are shown in Tables 4-9.

[0085] Table 4 RW water sample test table

[0086] Water quality index Detection result Water quality index Detection result TOC (mg / L) 525.4 COD (mg / L) 1709.8 UV 254 ]] 1.732 Conductivity (us / cm) 14060

[0087] Table 5 RW-MF water sample test table

[0088] Water quality index Detection result Water quality index Detection result TOC (mg / L) 442.7 COD (mg / L) 1241.68 UV 254 ]]> 1.326 Conductivity (us / cm) 6450

[0089] Table 6 RW-NF water sample test table

[0090] Water quality index Detection result Water quality index Detection result TOC (mg / L) 35.01 COD (mg / L) 20.14 UV 254 ]]> 0.1432 Conductivity (us / cm) 491

[0091] Table 7 Fe(VI)-HA water sample test table

[0092] Water quality index Detection result Water quality index Detection result TOC (mg / L) 364.9 COD (mg / L) 1154.12 UV 254 ]]> 0.7036 Conductivity (us / cm) 14060

[0093] Table 8 Fe(VI)-HA-MF water sample test table

[0094] Water quality index Detection result Water quality index Detection result TOC (mg / L) 263.1 COD (mg / L) 457.35 UV 254 ]] 0.5002 Conductivity (us / cm) 6500

[0095] Table 9 Fe(VI)-HA-NF water sample test table

[0096]

[0097]

[0098] For the above water samples, the removal rate of organic matter in each water sample is tested, and the test results are shown in Table 10.

[0099] Table 10

[0100]

[0101] As shown in Table 10, for the original water sample, the removal rate of each index is less than 30% after microfiltration membrane MF treatment, although the effluent effect is better after nanofiltration membrane NF treatment, the load on the nanofiltration membrane is larger, and the damage to the nanofiltration membrane is larger.

[0102] For the water sample after oxidation treatment and membrane treatment, the COD and UV 254 removal rate of the water sample after oxidation treatment can reach more than 70%, which can effectively reduce the membrane pollution during nanofiltration membrane NF treatment.

[0103] The original water sample and the water sample after hydroxylamine hydrochloride enhanced ferrate oxidation treatment are subjected to microfiltration treatment, and the membrane flux of the corresponding membrane after microfiltration treatment and nanofiltration treatment is tested, and the test results are shown in Table 10 and Table 11. Figure 11 and Figure 12 The results show that whether the microfiltration membrane or the nanofiltration membrane, the water sample after hydroxylamine hydrochloride enhanced ferrate oxidation treatment can effectively improve the membrane flux, which indicates that the high molecular weight organic matter is decomposed in the oxidation process, the content of the organic matter passing through the membrane hole increases, and the membrane blockage is obviously relieved.

[0104] It can be seen that the water quality after hydroxylamine hydrochloride enhanced ferrate oxidation treatment is filtered through the membrane, which can obviously improve the membrane flux, reduce the membrane surface pollution, greatly prolong the service life of the membrane, reduce the number of membrane replacement, and reduce the filtration cost.

[0105] The microfiltration membrane obtained after the different water samples are subjected to microfiltration treatment, and the nanofiltration membrane obtained after the water samples are subjected to microfiltration treatment and nanofiltration treatment are characterized by infrared (ATR-FITR), and the characterization results are shown in Table 12 and Table 13. Figure 13 and Figure 14 . Figure 13 The infrared curves of the original membrane (referred to as Virgin membrane), the membrane after the original water sample is filtered (referred to as RW), and the membrane after the water sample is filtered after oxidation treatment (referred to as Fe(VI)-HA) corresponding to the microfiltration membrane are shown in Table 12. Figure 14 The infrared curves of the original membrane (referred to as Virgin membrane), the membrane after the original water sample is filtered (referred to as RW), and the membrane after the water sample is filtered after oxidation treatment (referred to as Fe(VI)-HA) corresponding to the nanofiltration membrane are shown in Table 13.

[0106] From Figure 13 It can be seen that the characteristic peaks of the original membrane of the microfiltration membrane are: 3276 cm-1, 1663 cm-1, 1401 cm-1, 1172 cm-1, 1097 cm-1, 1066 cm-1, 568 cm-1. From Figure 14 It can be seen that the characteristic peaks of the original membrane of the nanofiltration membrane are: 3356 cm-1, 1363 cm-1, 1034 cm-1. The characteristic peaks of the two membranes are more obviously decreased after the water sample permeated through the membrane after oxidation treatment, which indicates that the thickness of the pollutants on the membrane after the water sample permeated through the membrane after oxidation treatment is lower than that of the original water sample permeated through the membrane.

[0107] The atomic force microscope images of the microfiltration membranes obtained after the different water samples were treated by microfiltration, and the nanofiltration membranes obtained after the water samples were treated by microfiltration and nanofiltration in turn, are shown in Figure 15 and Figure 16 . Figure 15 The atomic force microscope images of the original membrane (also known as blank membrane) corresponding to the microfiltration membrane, the membrane after the original water sample permeated through (abbreviated as RW), and the membrane after the water sample permeated through after oxidation treatment (abbreviated as Fe(VI)-HA) are shown in Figure 16 The atomic force microscope images of the original membrane (also known as blank membrane) corresponding to the nanofiltration membrane, the membrane after the original water sample permeated through (abbreviated as RW), and the membrane after the water sample permeated through after oxidation treatment (abbreviated as Fe(VI)-HA) are shown in.

[0108] From Figure 15 and Figure 16 It can be seen that the roughness of the membrane after the water sample permeated through is obviously higher than that of the blank membrane, but the roughness of the membrane after the water sample permeated through after oxidation treatment is lower than that of the membrane after the original water sample permeated through. The smaller the roughness in the atomic force microscope image is, the smoother the membrane surface is, which means higher thin film quality and better efficiency, indicating that the water sample after oxidation can effectively reduce membrane pollution.

[0109] The above merely describes the technical solutions of the present application for the purpose of facilitating the understanding of those skilled in the art, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A fracturing flowback fluid treatment process, characterized in that, The fracturing flowback fluid treatment process includes: coagulating the fracturing flowback fluid to obtain a coagulated solution; The coagulated solution was oxidized using a hydroxylamine hydrochloride-enhanced ferrate process to obtain an oxidized solution. The oxidation treatment fluid is subjected to microfiltration and nanofiltration in sequence to obtain purified water, thus completing the treatment of the fracturing flowback fluid.

2. The fracturing flowback fluid treatment process according to claim 1, characterized in that, The coagulant used in the coagulation treatment includes at least one of polyalumina (PAC) and polyacrylamide (PAM).

3. The fracturing flowback fluid treatment process according to claim 2, characterized in that, The dosage of the polymeric alumina (PAC) is 100 mg / L to 1000 mg / L; The dosage of polyacrylamide (PAM) is 10 mg / L to 30 mg / L.

4. The fracturing flowback fluid treatment process according to claim 2, characterized in that, The coagulation treatment of the fracturing flowback fluid to obtain a coagulated solution includes: Polyalumina (PAC) is added to the fracturing flowback fluid and stirred at a speed of 600 r / min-1000 r / min until homogeneous. Then, polyacrylamide (PAM) is added to the solution and stirred at a speed of 100 r / min-300 r / min until homogeneous. The solution is then allowed to stand to obtain the coagulated solution.

5. The fracturing flowback fluid treatment process according to any one of claims 1-4, characterized in that, The process of using hydroxylamine hydrochloride to enhance ferrate salts to oxidize the coagulation solution and obtain an oxidized solution includes: filtering the coagulation solution, then adding hydroxylamine hydrochloride to adjust the pH of the solution to neutral, and then adding ferrate salts dissolved in a phosphate-boric acid buffer solution to achieve the oxidation treatment of the coagulation solution.

6. The fracturing flowback fluid treatment process according to claim 5, characterized in that, The amount of ferrate used is 1 g / L to 5 g / L; The dosage of hydroxylamine hydrochloride is 10 mg / L to 20 mg / L.

7. The fracturing flowback fluid treatment process according to claim 6, characterized in that, The ratio of the amount of ferrate to the amount of hydroxylamine hydrochloride is 100:0.2-0.

8.

8. The fracturing flowback fluid treatment process according to claim 5, characterized in that, When the coagulated solution is oxidized using the hydroxylamine hydrochloride-enhanced ferrate process, the reaction temperature is 20℃~30℃ and the reaction time is 30min~100min.

9. The fracturing flowback fluid treatment process according to any one of claims 1-8, characterized in that, The microfiltration process uses a microfiltration membrane with a pore size of 0.1 micrometers to 10 micrometers.

10. The fracturing flowback fluid treatment process according to any one of claims 1-8, characterized in that, The nanofiltration process uses a nanofiltration membrane with a pore size of 0.1 nanometers to 10 nanometers.

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