Surfactant residual concentration measuring device and method

Abstract

The present invention discloses a device for measuring the residual concentration of a surfactant, which comprises: a container having a cavity for accommodating an experimental solution; a three-electrode system comprising a working electrode, a reference electrode and an auxiliary electrode, wherein the working electrode is a micron metal electrode, a nano metal electrode or a porous foam metal electrode; a bubble generator, which introduces bubbles into the container; and an electrochemical workstation, which is connected to the three-electrode system for communication, and the electrochemical workstation detects the cyclic voltammetry curve and / or the dynamic potential polarization curve of the working electrode. The present invention also discloses a method for measuring the residual concentration of a surfactant. The measurement result of the device and method for measuring the residual concentration of a surfactant of the present invention is sensitive to the concentration of the surfactant, and the entire experimental process does not require the addition of toxic chemicals, thereby avoiding interference from other ions; the experimental steps are simple, and the measurement results can be obtained quickly.

Description

Technical Field

[0001] The invention relates to the technical field of corrosion control of metal materials, and in particular to a device and method for measuring residual concentration of surfactant. Background Art

[0002] The production, storage and transportation of oil and gas usually face corrosion problems, which are generally controlled by adding corrosion inhibitors. However, the amount of corrosion inhibitor added is not only related to the corrosion inhibition effect, but also directly related to the economic benefits. The best corrosion control solution is to use an amount of corrosion inhibitor that can achieve the corrosion control effect and not add too much, which requires monitoring the residual concentration of corrosion inhibitor in the produced water. The methods for measuring the residual concentration of corrosion inhibitors reported in the literature are mainly through color developers, extractions and spectrophotometers. These methods have the disadvantages of complex operating steps, the measurement results are easily interfered by other ions in the produced water, and toxic chemicals may need to be added during the experiment.

[0003] The invention patent "Online detection method, detection device and circulating cooling water treatment control system for the concentration of scale inhibitors and corrosion inhibitors in circulating cooling water" (201610096311.1) invented a method for online detection of the concentration of scale inhibitors and corrosion inhibitors in circulating cooling water. The method adopts a cationic polyelectrolyte as a detection surfactant, and adds the detection surfactant to the circulating cooling water sample to be detected in an amount sufficient to react all the scale inhibitors and corrosion inhibitors in the circulating cooling water, mixes them thoroughly, and reacts for 15 to 20 minutes. Then, the absorbance value of the reacted circulating cooling water sample is detected at a wavelength of 400 to 600 nm, and the concentration of the scale inhibitors and corrosion inhibitors in the circulating cooling water is determined according to the absorbance value; the scale inhibitors and corrosion inhibitors include at least one of a polycarboxylic acid homopolymer, a polycarboxylic acid copolymer, a phosphine carboxylic acid homopolymer or a phosphine carboxylic acid copolymer. The cationic polyelectrolyte includes any one of dodecyl dimethyl benzyl ammonium chloride, hexadecyl trimethyl ammonium chloride, octadecyl trimethyl ammonium chloride or octadecyl dimethyl benzyl ammonium chloride. This method, like the colorimetric method, has the disadvantages of complicated operation steps and the measurement results are easily interfered by other ions in the circulating cooling water.

[0004] The utility model "A device for detecting the concentration of corrosion inhibitors in oilfield wastewater" (201820983295.2) invented a device for detecting the concentration of corrosion inhibitors in oilfield wastewater. By pulling the rod, the conical container is fixed or loosened in the groove under the action of the spring and the arc-shaped fixed card plate, and then the reduction motor is started. Under the linkage of the turntable, the rotating column, the rotating shaft, the swing rod, the fan gear and the rack, the oscillation block is driven to oscillate back and forth on the surface of the guide rod, so that the solution to be tested is fully and quickly foamed in the conical container. Finally, the amount of foam is read through the measuring scale, and the concentration of the corrosion inhibitor in oilfield wastewater can be quickly detected by comparison. Since the amount of foam generated by the corrosion inhibitor is closely related to the specific type and model of the corrosion inhibitor, some corrosion inhibitors generate very little foam and are insensitive to changes in the concentration of the corrosion inhibitor, and the corrosion inhibitor concentration on site is added at the ppm level, therefore, the amount of foam of the corrosion inhibitor cannot effectively characterize the concentration of the corrosion inhibitor. This method is only suitable for the case where only one type of corrosion inhibitor exists in the oilfield wastewater. In fact, other additives may be added in oilfield production, which may affect the foaming of wastewater. In addition, the concentration of corrosion inhibitors in oilfields is required to be at the ppm level. If a large amount of foaming occurs in the oilfield wastewater due to the addition of corrosion inhibitors, it will affect production. Such corrosion inhibitors are not allowed to be added in oilfields. Some oilfields have clear requirements in the corrosion inhibitor product indicators that no obvious foaming should occur.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] One of the purposes of the present invention is to provide a device and method for measuring the residual concentration of a surfactant, so as to improve the problem that the existing residual concentration measurement technology of a surfactant is easily interfered by other ions.

[0007] Another object of the present invention is to provide a device and method for measuring the residual concentration of a surfactant, thereby simplifying the operating steps for measuring the residual concentration of the surfactant.

[0008] Another object of the present invention is to provide a device and method for measuring the residual concentration of surfactant, so as to achieve a wider range of applications.

[0009] To achieve the above-mentioned purpose, according to the first aspect of the present invention, there is provided a device for measuring the residual concentration of a surfactant, which comprises: a container having a cavity for accommodating an experimental solution; a three-electrode system comprising a working electrode, a reference electrode and an auxiliary electrode, the working electrode being a micron metal electrode, a nano metal electrode or a porous foam metal electrode; a bubble generator for introducing bubbles into the container; and an electrochemical workstation, which is communicatively connected to the three-electrode system, and the electrochemical workstation detects the cyclic voltammetry curve and / or the potentiodynamic polarization curve of the working electrode.

[0010] Furthermore, in the above technical solution, one end of the bubble generator is connected to the gas source, and the other end is connected to the ventilation pipe, and the end of the ventilation pipe is provided with a ventilation hole section, and the ventilation hole section has multiple ventilation holes evenly distributed.

[0011] Furthermore, in the above technical solution, the vent pipe can move up and down so that the vent hole section is below or above the liquid surface of the experimental solution.

[0012] Furthermore, in the above technical solution, the vent hole section and the vent pipe are an integrated structure.

[0013] Furthermore, in the above technical solution, the vent hole section is detachably connected to the end of the ventilation pipe.

[0014] Furthermore, in the above technical solution, when the working electrode is a porous foam metal electrode, at least one section of the porous foam metal electrode is filled with a sealant.

[0015] Furthermore, in the above technical solution, the porous foam metal electrode is connected to the conductive wire via a hook-shaped end; and a conductive tape is provided at the connection between the hook-shaped end and the conductive wire.

[0016] Furthermore, in the above technical solution, an isolation sleeve is provided outside the porous foam metal electrode.

[0017] Furthermore, in the above technical solution, when the working electrode is a nano-metal electrode or a micro-metal electrode, the working electrode is fixed by a sealing material, and a protective cover is provided outside the sealing material.

[0018] Furthermore, in the above technical solution, the working electrode is a gold electrode, a platinum electrode or a stainless steel electrode, and the non-working surface of the working electrode is sealed with epoxy resin; the reference electrode is an Ag / AgCl electrode or a CuSO4 electrode; and the auxiliary electrode is a platinum electrode or a stainless steel electrode.

[0019] Furthermore, in the above technical solution, the auxiliary electrode is a circular electrode.

[0020] Furthermore, in the above technical solution, the diameter of the circular electrode is greater than the distance between the working electrode and the reference electrode.

[0021] Furthermore, in the above technical solution, the distances from the working electrode to the circumference of the auxiliary electrode are the same.

[0022] Furthermore, in the above technical solution, the auxiliary electrode is provided with an electrode connection line, and the electrode connection line is perpendicular to the auxiliary electrode.

[0023] Furthermore, in the above technical solution, a hollow tube is provided outside the electrode connecting wire, and the length of the hollow tube is smaller than the length of the electrode connecting wire.

[0024] Furthermore, in the above technical solution, the material of the electrode connection wire is the same as that of the auxiliary electrode, and the hollow tube is made of non-metallic material.

[0025] Furthermore, in the above technical solution, epoxy resin is filled between the electrode wire and the hollow tube.

[0026] Furthermore, in the above technical solution, the electrochemical workstation is a direct current measurement system.

[0027] Furthermore, in the above technical solution, the surfactant is a corrosion inhibitor, a scale inhibitor, a bactericide or a hydrate inhibitor.

[0028] Furthermore, in the above technical solution, the working electrode is provided with an endoscope.

[0029] According to the second aspect of the present invention, the present invention provides a method for measuring the residual concentration of surfactant, which comprises at least the following steps: preparing standard surfactant solutions of different concentrations; introducing gas into the standard surfactant solutions to achieve the simulation conditions of the actual environment; obtaining the cyclic voltammetry curves or the potentiodynamic polarization curves of the standard surfactant solutions of different concentrations to obtain a standard curve; introducing gas into the surfactant solution to be detected to achieve the simulation conditions of the actual environment; obtaining the cyclic voltammetry curve or the potentiodynamic polarization curve of the surfactant solution to be detected to obtain a detection curve; comparing the detection curve with the standard curve to obtain the residual concentration of surfactant in the surfactant solution to be detected.

[0030] Furthermore, in the above technical solution, the method for measuring the residual concentration of surfactant adopts a residual concentration measuring device of surfactant as in any one of the above technical solutions.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The measurement results are sensitive to the concentration of surfactants. No toxic chemicals need to be added during the entire experiment, avoiding interference from other ions.

[0033] 2. The experimental steps are simple and the measurement results can be obtained quickly.

[0034] 3. It has a wider application scope and is suitable for the concentration measurement of various surfactants in aqueous solutions and field return fluids, and can also be used to measure the concentration of multiple surfactants in a certain proportion.

[0035] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, and to make the above and other purposes, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the structure of a device for measuring residual concentration of surfactant according to one embodiment of the present invention.

[0037] Figure 2 is a schematic diagram of a porous metal foam working electrode according to one embodiment of the present invention.

[0038] Figure 3 is a schematic diagram of a working electrode according to another embodiment of the present invention, wherein the working electrode is a micron metal electrode or a nano metal electrode.

[0039] Figure 4 is a schematic diagram of an auxiliary electrode according to an embodiment of the present invention.

[0040] Figure 5 FIG. 1 is a schematic top view of an auxiliary electrode according to an embodiment of the present invention.

[0041] Description of main reference numerals:

[0042] 10-container, 11-experimental solution, 21-working electrode, 211-porous foam metal electrode, 2111-working surface, 2112-sealant, 2113-isolating sleeve, 2114-conductive wire, 2115-hook-shaped end, 2116-conductive tape, 212-micron (or nano) metal electrode, 2121-sealing material, 2122-protective sleeve, 2123-working electrode connection, 2124-fixing sleeve, 22-reference electrode, 23-auxiliary electrode, 231-electrode connection, 232-hollow tube, 233-epoxy resin, 30-bubble generator, 31-vent tube, 311-vent section, 3111-vent, 40-electrochemical workstation, 50-endoscope. DETAILED DESCRIPTION

[0043] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0044] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0045] In this document, for the convenience of description, spatial relative terms such as "below", "below", "down", "above", "above", "upper", etc. may be used to describe the relationship between one element or feature and another element or feature in the accompanying drawings. It should be understood that the spatial relative terms are intended to include different orientations of the object in use or operation in addition to the orientation depicted in the figure. For example, if the object in the figure is turned over, the element described as being "below" or "below" other elements or features will be oriented "above" the element or feature. Therefore, the exemplary term "below" can include both the below and above directions. Objects may also have other orientations (rotated 90 degrees or other orientations) and the spatial relative terms used in this document should be interpreted accordingly.

[0046] In this document, the terms "first", "second", etc. are used to distinguish two different elements or parts, and are not used to limit a specific position or relative relationship. In other words, in some embodiments, the terms "first", "second", etc. can also be interchangeable.

[0047] The surfactant residual concentration measuring device of the present invention measures the surfactant residual concentration in water by gas nucleation and electrochemical measurement methods, and can also be used to measure the residual concentration of other surfactants in water. In aqueous solutions containing corrosion inhibitors and surfactants of different concentrations, the surface tension of the aqueous solutions is different, and the nucleation of bubbles generated by cathode reactions is also different, resulting in differences in the diffusion control processes of cyclic voltammetry curves and cathode polarization curves. The surfactant residual concentration measuring device of the present invention converts the change in the degree of supersaturation required for bubble nucleation into an electrochemical signal, and characterizes different corrosion inhibitor or surfactant concentrations in water through the cathode limiting current.

[0048] like Figure 1 As shown, in the surfactant residual concentration measuring device according to a specific embodiment of the present invention, the container 10 has a cavity for accommodating the experimental solution 11. The three-electrode system includes a working electrode 21, a reference electrode 22 and an auxiliary electrode 23. The working electrode 21 is an unconventional electrode. Exemplarily, the working electrode 21 can be a micron metal electrode, a nano metal electrode or a porous foam metal electrode. The bubble generator 30 can introduce bubbles into the container 10. The electrochemical workstation 40 is communicatively connected with the working electrode 21, the reference electrode 22 and the auxiliary electrode 23, and the electrochemical workstation 40 can detect the cyclic voltammetry curve and / or the dynamic potential polarization curve of the working electrode 21.

[0049] Further, in one or more exemplary embodiments of the present invention, one end of the bubble generator 30 is connected to a gas source (not shown in the figure), and the other end is connected to a vent pipe 31. A vent section 311 is provided at the end of the vent pipe 31. The vent section 311 has multiple tiny vents 3111 evenly distributed thereon to ensure the uniformity of the bubbles. Exemplarily, the gas source may be a gas cylinder, but the present invention is not limited thereto. The gas source is the gas required for the experiment, such as CO2 and H2S corrosion simulating the oil and gas field environment. Generally, a certain CO2 and H2S partial pressure or a certain O2 content condition is required. The bubble generator 30 can keep the gas pressure introduced into the container 10 and the size of the bubbles stable. Further, in one or more exemplary embodiments of the present invention, the vent pipe 31 can move up and down so that the vent section 311 can be below or above the liquid level of the experimental solution 11.

[0050] Further, in one or more exemplary embodiments of the present invention, the vent segment 311 and the vent pipe 31 may be an integral structure. Further, in one or more exemplary embodiments of the present invention, the vent segment 311 is detachably connected to the end of the vent pipe 31, and illustratively, the vent pipe 31 and the vent segment 311 may be connected by threads, but the present invention is not limited thereto.

[0051] Furthermore, in one or more exemplary embodiments of the present invention, the working electrode 21 is an unconventional electrode, and its surface may be a micron or nanometer metal, or a porous foam metal. The working electrode 21 may be a gold electrode, a platinum electrode, a stainless steel electrode, or other metal material electrode suitable for use in an actual system. It should be understood that the present invention is not limited thereto. Figure 2 As shown, in one or more embodiments of the present invention, the working electrode is a porous foam metal electrode 211, the working surface 2111 of the porous foam metal electrode 211 is a porous structure, and the non-working surface is sealed with a sealant 2112. Exemplarily, the sealant can be an epoxy resin. Exemplarily, an isolation sleeve 2113 is provided on the outer surface of the porous foam metal electrode 211, and the isolation sleeve 2113 can be a heat shrink tape or other non-metallic material; the conductive wire 2114 is connected to the porous foam metal electrode 211 through a hook-shaped end 2115, and is connected through a conductive tape 2116, which can achieve the effect of point conduction on the one hand, and fix the hook-shaped end 2115 and the porous foam metal electrode 211 at the same time. Figure 3As shown, in one or more embodiments of the present invention, the working electrode is a micron (or nanometer) metal electrode 212, whose working surface is a micron (or nanometer) level working surface, and the micron (or nanometer) metal electrode 212 is fixed by a sealing material 2121, and a protective sleeve 2122 is used outside the sealing material 2121 to protect the platinum material or gold material part of the entire micron (or nanometer) metal electrode 212 to avoid direct contact with the experimental solution. The working electrode connection line 2123 is connected to the micron (or nanometer) metal electrode 212, and a fixing sleeve 2124 is provided at the connection, which maintains electrical connection on the one hand, and fixes the platinum material or gold material of the micron (or nanometer) metal electrode 212 on the other hand.

[0052] Further, in one or more exemplary embodiments of the present invention, the reference electrode 22 is an Ag / AgCl electrode or a CuSO 4 electrode.

[0053] Furthermore, in one or more exemplary embodiments of the present invention, the auxiliary electrode 23 may be a corrosion-resistant electrode such as a platinum electrode or a stainless steel electrode. Figure 4 and Figure 5 As shown, in one or more embodiments of the present invention, the auxiliary electrode 23 is a circular electrode. Exemplarily, the diameter of the circular electrode is greater than the distance between the working electrode 21 and the reference electrode 22. The distance from the working electrode 21 to the circumference of the auxiliary electrode 23 is substantially the same. The auxiliary electrode 23 is provided with an electrode connection line 231 perpendicular thereto, and the electrode connection line 231 can be connected by welding or twisting, etc., to maintain the electrical connection between the auxiliary electrode 23 and the electrode connection line 231. In order to maintain a relatively fixed position between the auxiliary electrode 23 and the electrode connection line 231, a hollow tube 232 is provided on the outer sleeve of the electrode connection line 231, and the length of the hollow tube 232 is 3 to 5 cm shorter than the length of the electrode connection line 231. Exemplarily, the material of the electrode connection line 231 is the same as that of the auxiliary electrode 23, and the hollow tube 232 is made of a corrosion-resistant non-metallic material, such as glass or PVC material, but the present invention is not limited thereto. The bottom of the hollow tube 232 is flush with the electrode connection line 231 , and epoxy resin 233 can be filled between the two. The cured epoxy resin 233 enables the auxiliary electrode 23 and the electrode connection line 231 to remain vertical and achieve electrical connection.

[0054] Further, in one or more exemplary embodiments of the present invention, the electrochemical workstation 40 is unconventional and has only a DC measurement system. The electrochemical workstation 40 can detect the cyclic voltammetry curve (which represents the critical current density) and the potentiodynamic polarization curve (which represents the limiting current) of the working electrode 21 in the experimental solution 11.

[0055] Further, in one or more exemplary embodiments of the present invention, the surfactant may be a corrosion inhibitor, a scale inhibitor, a bactericide or a hydrate inhibitor, but the present invention is not limited thereto.

[0056] Further, in one or more exemplary embodiments of the present invention, the working electrode 21 is provided with an endoscope 50, and the endoscope 50 can observe the nucleation and rupture process of bubbles on the surface of the working electrode 21. The nucleation and rupture process of bubbles is characterized by limiting current.

[0057] In a specific embodiment of the present invention, the method for measuring the residual concentration of surfactant includes at least the following steps: preparing standard surfactant solutions of different concentrations; introducing gas into the standard surfactant solutions to achieve the simulation conditions of the actual environment; obtaining the cyclic voltammetry curves or the potentiodynamic polarization curves of the standard surfactant solutions of different concentrations to obtain a standard curve; introducing gas into the surfactant solution to be detected to achieve the simulation conditions of the actual environment; obtaining the cyclic voltammetry curve or the potentiodynamic polarization curve of the surfactant solution to be detected to obtain a detection curve; comparing the detection curve with the standard curve to obtain the residual concentration of surfactant in the surfactant solution to be detected.

[0058] Combination Figure 1 to Figure 5 As shown, in one or more embodiments of the present invention, the method for measuring the residual concentration of surfactant is implemented by using a device for measuring the residual concentration of surfactant as described in any one of the above technical solutions.

[0059] The following is a more detailed description of the surfactant residual concentration measuring device and method of the present invention by way of specific embodiments. It should be understood that the present invention is not limited thereto.

[0060] Example 1

[0061] In this embodiment, the surfactant residual concentration measuring device of the present invention (refer to Figure 1 The present invention is to measure the residual concentration of corrosion inhibitor in the produced water of the oil field by using the method shown in the figure. In this embodiment, the working electrode is a micron metal electrode.

[0062] Add the experimental solution 11 containing different concentrations of corrosion inhibitors into the container 10, immerse the vent section 311 of the vent pipe 31 below the liquid surface of the experimental solution 11, and place the working electrode 21, the reference electrode 22 and the auxiliary electrode 23 of the three-electrode system into the experimental solution 11. Turn on the bubble generator 30 to pass CO2 and H2S gas into the experimental solution 11. The vent 3111 generates uniform bubbles, which are evenly distributed in the experimental solution 11, thereby discharging oxygen in the experimental solution 11. After the ventilation reaches the simulation conditions of the actual environment, lift the vent pipe 31 so that the vent section 311 is in the gas phase space above the liquid surface of the experimental solution 11, and continue to ventilate.

[0063] The electrochemical workstation 40 is used to perform multiple scans using cyclic voltammetry until the curves in the cathode scanning direction overlap, and the critical current values ​​under different corrosion inhibitor concentrations are listed to draw a standard curve. For oilfield produced water samples with unknown corrosion inhibitor concentrations, the critical current value is measured using the above method, and the detection curve is obtained and compared with the standard curve to obtain the residual concentration of the corrosion inhibitor in the oilfield produced water.

[0064] Example 2

[0065] In this embodiment, the surfactant residual concentration measuring device of the present invention (refer to Figure 1 The present invention is to measure the residual concentration of corrosion inhibitor in circulating water of an oil refinery by using a method as shown in the figure. In this embodiment, the working electrode is a nano-metal electrode.

[0066] Add the experimental solution 11 containing different concentrations of corrosion inhibitors into the container 10, immerse the vent section 311 of the vent pipe 31 below the liquid surface of the experimental solution 11, and place the working electrode 21, the reference electrode 22 and the auxiliary electrode 23 of the three-electrode system into the experimental solution 11. Turn on the bubble generator 30 to pass O2 and other gases into the experimental solution 11. The vent 3111 generates uniform bubbles, which are evenly distributed in the experimental solution 11, so that the experimental solution 11 reaches a certain oxygen content. After the ventilation reaches the simulation conditions of the actual environment, lift the vent pipe 31 so that the vent section 311 is in the gas phase space above the liquid surface of the experimental solution 11, and continue to ventilate.

[0067] The cathode curve is measured by the electrochemical workstation 40 using the method of dynamic potentiodynamic curve measurement, and the limiting current values ​​under different corrosion inhibitor concentrations are listed to draw a standard curve. For a refinery circulating water sample with unknown corrosion inhibitor concentration, the limiting current value is measured using the above method to obtain a detection curve and compare it with the standard curve to obtain the residual concentration of corrosion inhibitor in the refinery circulating water.

[0068] Example 3

[0069] In this embodiment, the surfactant residual concentration measuring device of the present invention (refer to Figure 1 ) and method are used to measure the residual concentration of corrosion inhibitor in the produced water of shale gas fields. In this embodiment, the working electrode is a porous foam metal electrode 211, and a sealant 2112 is used to seal the area about 0.5 to 0.8 mm away from the working surface 2111 to prevent the experimental solution from entering other parts of the porous foam metal electrode 211. Due to the porous structure of the electrode, the sealant 2112 only fills the pores of the electrode and does not affect the conductivity of the working electrode.

[0070] Add the experimental solution 11 containing different concentrations of corrosion inhibitors into the container 10, immerse the vent section 311 of the vent pipe 31 below the liquid surface of the experimental solution 11, and place the working electrode 21, the reference electrode 22 and the auxiliary electrode 23 of the three-electrode system into the experimental solution 11. Turn on the bubble generator 30 to pass CO2 and other gases into the experimental solution 11. The vent 3111 generates uniform bubbles, which are evenly distributed in the experimental solution 11, thereby discharging oxygen in the experimental solution 11. After the ventilation reaches the simulation conditions of the actual environment, lift the vent pipe 31 so that the vent section 311 is in the gas phase space above the liquid surface of the experimental solution 11, and continue to ventilate.

[0071] The cathode curve is measured by the electrochemical workstation 40 using the method of dynamic potentiodynamic curve measurement, and the limiting current values ​​under different corrosion inhibitor concentrations are listed to draw a standard curve. For shale gas field produced water samples with unknown corrosion inhibitor concentrations, the limiting current value is measured using the above method to obtain a detection curve and compare it with the standard curve to obtain the residual concentration of corrosion inhibitor in the shale gas field produced water.

[0072] Example 4

[0073] In this embodiment, the surfactant residual concentration measuring device of the present invention (refer to Figure 1 The present invention provides a method for measuring the residual concentration of corrosion inhibitor in oilfield reinjection water. In this embodiment, the working electrode is a nano-metal electrode.

[0074] Add the experimental solution 11 containing different concentrations of corrosion inhibitors into the container 10, immerse the vent section 311 of the vent pipe 31 below the liquid surface of the experimental solution 11, and place the working electrode 21, reference electrode 22 and auxiliary electrode 23 of the three-electrode system into the experimental solution 11. Turn on the bubble generator 30 to pass N2 and other gases into the experimental solution 11. The vent 3111 generates uniform bubbles, which are evenly distributed in the experimental solution 11, thereby discharging oxygen in the experimental solution 11. After the ventilation reaches the simulation conditions of the actual environment, lift the vent pipe 31 so that the vent section 311 is in the gas phase space above the liquid surface of the experimental solution 11, and continue to ventilate.

[0075] The electrochemical workstation 40 is used to scan multiple times using cyclic voltammetry until the curves in the cathode scanning direction overlap, and the critical current values ​​under different corrosion inhibitor concentrations are listed to draw a standard curve. For oilfield reinjection water samples with unknown corrosion inhibitor concentrations, the critical current value is measured using the above method, and the detection curve is obtained and compared with the standard curve to obtain the residual concentration of the corrosion inhibitor in the oilfield reinjection water.

[0076] Example 5

[0077] In this embodiment, the surfactant residual concentration measuring device of the present invention (refer to Figure 1) and method are used to measure the residual concentration of corrosion inhibitor in a water treatment environment. In this embodiment, the working electrode is a porous foam metal electrode 211, and a sealant 2112 is used to seal the area about 0.5 to 0.8 mm away from the working surface 2111 to prevent the experimental solution from entering other parts of the porous foam metal electrode 211. Due to the porous structure of the electrode, the sealant 2112 only fills the pores of the electrode and does not affect the conductivity of the working electrode.

[0078] Add the experimental solution 11 into the container 10, the experimental solution 11 contains corrosion inhibitors of different concentrations, immerse the vent section 311 of the vent pipe 31 below the liquid surface of the experimental solution 11, and place the working electrode 21, the reference electrode 22 and the auxiliary electrode 23 of the three-electrode system into the experimental solution 11. Turn on the bubble generator 30 to pass O2 gas into the experimental solution 11. The vent 3111 generates uniform bubbles, which are evenly distributed in the experimental solution 11, so that the experimental solution 11 reaches a certain oxygen concentration. After the ventilation reaches the simulation conditions of the actual environment, lift the vent pipe 31 so that the vent section 311 is in the gas phase space above the liquid surface of the experimental solution 11, and continue to ventilate.

[0079] The cathode curve is measured by the electrochemical workstation 40 using the method of dynamic potentiodynamic curve measurement, the limiting current values ​​under different corrosion inhibitor concentrations are listed, and the standard curve is drawn. For water treatment environment samples with unknown corrosion inhibitor concentrations, the limiting current value is measured using the above method, and the detection curve is obtained and compared with the standard curve to obtain the residual concentration of the corrosion inhibitor in the water treatment environment.

[0080] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. Any simple modifications, equivalent changes and modifications made to the above exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A surfactant residual concentration measuring device, characterized in that: It is used to convert the change of supersaturation required for bubble nucleation into electrochemical signals, and characterize the surfactant concentration in the solution through the cathode limiting current, including: A container having a cavity for containing a test solution; A three-electrode system, comprising a working electrode, a reference electrode and an auxiliary electrode, wherein the working electrode is a micron metal electrode, a nano metal electrode or a porous foam metal electrode; the cathode limiting current is used to characterize the nucleation and rupture detachment process of bubbles on the surface of the working electrode, thereby characterizing the surfactant concentration in the solution; a bubble generator, which introduces bubbles into the container, and when the ventilation reaches the simulation conditions of the actual environment, continuously ventilates the gas phase space above the liquid surface of the experimental solution; and An electrochemical workstation is connected to the three-electrode system for detecting a potentiodynamic polarization curve of the working electrode.

2. The surfactant residual concentration measuring device according to claim 1, characterized in that: One end of the bubble generator is connected to a gas source, and the other end is connected to a ventilation pipe. The end of the ventilation pipe is provided with a ventilation hole section, and the ventilation hole section has a plurality of ventilation holes evenly distributed.

3. The surfactant residual concentration measuring device according to claim 2, characterized in that: The vent tube can move up and down so that the vent hole section is below or above the liquid level of the experimental solution.

4. The surfactant residual concentration measuring device according to claim 3, characterized in that: The vent hole section and the vent pipe are an integral structure.

5. The surfactant residual concentration measuring device according to claim 3, characterized in that: The vent section is detachably connected to the end of the vent tube.

6. The surfactant residual concentration measuring device according to claim 1, characterized in that: When the working electrode is a porous foam metal electrode, at least one section of the porous foam metal electrode is filled with sealant.

7. The surfactant residual concentration measuring device according to claim 6, characterized in that: The porous foam metal electrode is connected to the conductive wire via a hook-shaped end; a conductive tape is provided at the connection between the hook-shaped end and the conductive wire.

8. The surfactant residual concentration measuring device according to claim 6, characterized in that: An isolation sleeve is arranged outside the porous foam metal electrode.

9. The surfactant residual concentration measuring device according to claim 1, characterized in that: When the working electrode is a nano-metal electrode or a micro-metal electrode, the working electrode is fixed by a sealing material, and a protective cover is provided outside the sealing material.

10. The surfactant residual concentration measuring device according to claim 1, characterized in that: The working electrode is a gold electrode, a platinum electrode or a stainless steel electrode, and the non-working surface of the working electrode is sealed with epoxy resin; the reference electrode is an Ag / AgCl electrode or a CuSO4 electrode; and the auxiliary electrode is a platinum electrode or a stainless steel electrode.

11. The surfactant residual concentration measuring device according to claim 1, characterized in that: The auxiliary electrode is a circular electrode.

12. The surfactant residual concentration measuring device according to claim 11, characterized in that: The diameter of the circular electrode is greater than the distance between the working electrode and the reference electrode.

13. The surfactant residual concentration measuring device according to claim 11, characterized in that: The distances from the working electrode to the circumference of the auxiliary electrode are the same.

14. The surfactant residual concentration measuring device according to claim 11, characterized in that: The auxiliary electrode is provided with an electrode connection line, and the electrode connection line is perpendicular to the auxiliary electrode.

15. The surfactant residual concentration measuring device according to claim 14, characterized in that: The electrode connecting wire is outer-cased with a hollow tube, and the length of the hollow tube is smaller than the length of the electrode connecting wire.

16. The surfactant residual concentration measuring device according to claim 15, characterized in that: The material of the electrode connection wire is the same as that of the auxiliary electrode, and the hollow tube is made of non-metallic material.

17. The surfactant residual concentration measuring device according to claim 16, characterized in that: Epoxy resin is filled between the electrode connection wire and the hollow tube.

18. The surfactant residual concentration measuring device according to claim 1, characterized in that: The electrochemical workstation is a direct current measurement system.

19. The surfactant residual concentration measuring device according to claim 1, characterized in that: The surfactant is a corrosion inhibitor, a scale inhibitor, a bactericide or a hydrate inhibitor.

20. The surfactant residual concentration measuring device according to claim 1, characterized in that: The working electrode is provided with an endoscope.

21. A method for measuring residual concentration of surfactant, characterized in that: The surfactant residual concentration measuring device according to any one of claims 1 to 20 comprises at least the following steps: Prepare standard surfactant solutions of different concentrations; Aeration is introduced into the standard surfactant solution, and after reaching the simulated conditions of the actual environment, the gas phase space above the liquid surface of the solution is continuously ventilated; Obtaining potentiodynamic polarization curves of the standard surfactant solutions of different concentrations to obtain a standard curve; A gas is introduced into the surfactant solution to be tested, and after reaching the simulated conditions of the actual environment, the gas phase space above the liquid surface of the solution is continuously ventilated; Obtaining a potentiodynamic polarization curve of the surfactant solution to be detected to obtain a detection curve; The detection curve is compared with the standard curve to obtain the residual concentration of the surfactant in the surfactant solution to be detected; the nucleation and rupture and detachment process of the bubbles on the surface of the working electrode is characterized by the cathode limiting current, thereby characterizing the surfactant concentration in the solution.

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