JP3130758B2 - Cloud point measurement method and cloud point meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cloud point measuring method and a cloud point meter useful therefor, and more particularly to a method for measuring the solid content of petroleum products such as light oil and other chemical industrial liquid products in the petroleum industry. The present invention relates to a cloud point measuring method and a cloud point meter for measuring clouding due to precipitation or separation, removal of water and other state changes.

[0002]

2. Description of the Related Art Paraffin is contained in light oil, which is one of products in the oil refining process. Since the paraffin content is solid at around room temperature, when the paraffin content in the gas oil increases, the fluidity of the gas oil decreases under low temperature conditions in winter. When a sample of such a petroleum product such as light oil or lubricating oil is cooled by a prescribed method, a point at which paraffin precipitates or separates and the entire sample container starts to become cloudy is called a cloud point. Similar phenomena exist for plasticizers and surfactants. Cloud point measurements are important as a winter petroleum product standard. In addition, there are situations where many chemical products require measurement of solids precipitation upon cooling.

[0003] JIS K 2269 specifies a pour point for crude oil and petroleum products and a cloud point test method for petroleum products. According to the outline of the cloud point test method, "a 45 ml sample taken in a test tube is put into an outer tube of a cooling bath and cooled by a specified method.
Each time the temperature of the sample decreases by 1 ° C., the test tube is taken out, and the temperature at which the sample bottom becomes cloudy is defined as the cloud point. It is described. Furthermore, as a remark, it states that "An automatic cloud point tester may be used. However, it is used after confirming that there is no significant difference from the results obtained by this test method according to JIS Z8402." Have been. As a test device, a cooling tube equipped with a test tube in which a sample thermometer is vertically fixed by a cork stopper, an outer tube having a bottom disk made of cork or felt for accommodating the test tube, and a thermometer for cooling solution A bath is provided. The test tube is moved into and out of the outer tube via an annular gasket closely attached to the test tube.
An annular gasket closely attached to the periphery of the test tube loosely abuts the outer tube to vertically support the test tube in the outer tube. The test procedure is as follows: (1) Keep the sample at least 14 ° C above the expected cloud point. (2) Pour the sample up to the height of the marked line (center) of the test tube. (3) Seal the test tube with a cork stopper equipped with a thermometer. At this time, the thermometer stands upright at the center of the test tube, and its tip touches the bottom of the test tube. (4) Place the test tube with the annular gasket in the outer tube with the bottom disk at the bottom. (5) Place the outer tube containing the test tube in the first cooling bath, and vertically support the outer tube so that the outer tube does not come out of the cooling solution by more than 25 mm. (6) When the sample temperature reaches near the expected cloud point, remove the test tube from the outer tube promptly every 1 ° C and not to shake the sample, and check whether the bottom of the sample has fogged. Return. (7) Repeat this operation and record the thermometer reading when the first clear cloud or haze is found on the bottom of the sample. (If no fogging is observed even when the sample temperature reaches 10 ° C, transfer the test tube to the outer tube of the lower temperature second cooling bath. Even if the sample temperature reaches -7 ° C, no fogging is observed. If not, transfer the test tube to the outer tube of the lower temperature third cooling bath.) Thus, the laborious operation of carefully inserting and removing the test tube from the outer tube by hand is repeated many times. It needs to be repeated. Similar regulations exist in the United States.

As an automatic cloud point tester, in the case of petroleum products, a container containing a sample of about 50 cc is placed in a cooling bath.
After cooling at a cooling rate of 2 ° C / min, the precipitation state of paraffin is detected by a light absorption method or a light scattering method. This automatic cloud point test method is a method that follows the principle of cloud point measurement itself, but the temperature uniformity of the object to be detected is not necessarily guaranteed due to the large capacity of the sample collection container, and the required room temperature- It takes a long time to cool down to 20 ° C., and in addition to a long measurement time, a sample has to be collected in a large container, which is troublesome, requires a long working time, and is troublesome. Detection by the light absorption method or the light scattering method, which is determined based on a certain amount of precipitation, lacked accuracy. Each measurement took about 60 minutes. SUMMARY OF THE INVENTION It is an object of the present invention to develop a new technique for more accurately and conveniently measuring the cloud point of petroleum products more easily and quickly.

[0005]

As a highly accurate particle detection method utilizing light, there is a method utilizing diffraction or scattering of laser light. This method is employed, for example, for measuring impurity particles in ultrapure water or high-purity chemical used in the semiconductor manufacturing process, measuring the particle size distribution of powder, and the like. When a particle to be measured is irradiated with a monochromatic, parallel beam laser beam, a light intensity pattern of diffracted / scattered light is generated spatially.
This light intensity pattern changes depending on the size of the particles. For example, taking light scattering as an example, when the particle diameter is larger than the wavelength of the incident laser light, the forward component of the scattered light becomes dominant, and the diffracted / scattered light emitted from the particles concentrates in a small area in front (forward). scattering). On the other hand, when the particle diameter becomes smaller than the laser wavelength, lateral and backward scattering occurs in addition to forward scattering, so that the diffracted / scattered light emitted from the particles spreads. Therefore, the existence of the fine particles and the particle diameter thereof can be known by inputting light into the measurement target and observing the light intensity distribution pattern of the emitted light.

The inventor tried to put the sample oil in a transparent sample cell and cool the entire sample cell to near the cloud point in a cooling bath while irradiating the sample oil with visible laser light. As a result, at the cloud point, first, light scattering occurs due to the precipitated fine particles generated in the liquid, and then deposits occur on the cell wall and the like, and thereafter, the deposits are thickly deposited, which impedes the transmission of laser light. Up to. It was also found that even when the cooling rate of the cell was increased, the generation of the precipitated fine particles occurred at a constant temperature. Therefore, it was found that the cloud point can be accurately measured by detecting the appearance of the fine particles at an early stage.

The measuring apparatus used in the conventional laser diffraction / scattering method includes a laser light source having a high light intensity, an optical lens (collimator) for converting a laser beam into a parallel beam, and a sample such as a liquid containing particles. A relatively large off-line meter mainly including a transparent sample cell for storage, a detection optical system for detecting light emitted from the sample cell, and the like is mainly used. Such an apparatus requires precise optical axis alignment of various optical systems. In addition, since the light from the light source enters the sample cell and detects the light emitted from the sample cell, it is important to secure sufficient input and output light intensities to achieve accurate measurement. An optical system for narrowing the light, measures to prevent scattering at the sample cell / sample interface, and the like are required. In the cloud point measurement of petroleum products, it is necessary to provide a mechanism for cooling the entire sample cell while precisely controlling the temperature to a temperature at which fine particles are precipitated in the sample oil.

The present inventors have developed a sensor head which can further reduce the functions of the above-mentioned conventional offline measuring instrument, realize high-precision temperature control, and can be used not only offline but also online. The examination was repeated.
As a result, it was concluded that the combination of the waveguide type sensor to which the optical fiber was connected and the cooling mechanism or the heating mechanism was optimal for this purpose. As a result of the trial production, good operation performance was confirmed.

That is, according to the present invention, a sample to be measured is cooled or heated in a predetermined temperature range while light is incident on the sample to be measured, and forward scattering of incident light due to precipitation of a precipitate in the sample to be measured. A cloud point is measured by detecting light from an exit path, and the entrance path and the exit path are waveguides having a waveguide structure on a substrate. Includes a plurality of exit paths for detecting the forward scattered light from the detection area, and an entrance path for entering light into the detection area, wherein the entrance path and the exit path are waveguides having a waveguide structure on the substrate, A cloud point meter comprising a cooling means or a heating means in contact with the waveguide, wherein the detection area is concave. Or the heating means is placed on the heat sink By Peltier elements, to provide a cloud point meter, wherein the heat exchanger by circulating a refrigerant, or a cryostat.

This cloud point meter has a waveguide having a waveguide structure composed of an incident path 6 and a plurality of output paths 7, 7 ', 7 "that intersect on a substrate. The region including the intersection of the entrance path and the exit path is formed in a concave shape (FIG. 1) .In this cloud point meter, the concave portion on the detection surface becomes a detection area. Incident light that has entered and propagated through the incident path enters the detection area with a certain spread from the end face of the incident path in the concave portion.The incident light passes through the sample above the cloud point (FIG. 1). (a)), the sample is cooled and reaches the cloud point, and when precipitated fine particles are generated in the detection area, the incident light is again incident on the exit path by light scattering or the like and is detected (FIG. 1).
(b)). For example, in the case of light scattering, a forward scattered light component is incident on an output path arranged in a direction opposite to the incident path, and is detected from the output optical fiber. Similarly, the side scattered light component is detected from the outgoing path located on the side of the incident path, and the backscattered component is detected from the outgoing path located on the same side as the incident path. By detecting the emitted light, the presence of the precipitated fine particles, that is, the cloud point can be detected, and the light intensity distribution of the front, side, and rear components of the scattered light can be measured. The temperature at this point is read from a temperature measuring element attached to the junction between the cooling or heating means and the sensor substrate.

FIG. 2 is an exploded perspective view of a specific example of the cloud point meter according to the present invention. Cloud point meter 1 is a waveguide type sensor 2
And cooling or heating means 3 arranged in contact therewith (here shown separately for clarity). The waveguide sensor 2 has a concave detection surface (liquid contact surface) 4 for petroleum products such as light oil and other chemical products M to be measured. Then, on the substrate 5, an incident path 6, a plurality of output paths 7, 7 ′, and 7 ″, and a light incident end face 6 a formed on the concave detection surface 4.
And a light-emitting end face 7a.
The plurality of outgoing paths are disposed in a direction opposite to the incoming path 6 for detecting the forward scattered light component of the incident light due to the precipitated fine particles.
7 ", an emission path 7 'arranged laterally to the incidence path 6 for detecting the side scattered light component, and an emission path 7 located on the same side as the incidence path 6 for detecting the back scattered component.

At the entrance of the entrance path 6, an entrance optical fiber 10 for entering light into the entrance path 6, and at the exit of each exit path, an exit optical fiber 11, for receiving exit light from each exit path, 11 ', 11 "are attached. The input optical fiber 10 and the output optical fiber 11, 11', 11" are connected to the waveguide layer 9 via the respective optical fiber connection base 12 and the optical fiber array connection base 12 '. They are connected to the entrance path 6 and the exit paths 7, 7 ', 7 ", respectively. Incident optical fiber
Reference numeral 10 is connected to a laser light source such as a semiconductor laser light source, a He-Ne laser, or a semiconductor laser. The outgoing optical fibers 11, 11 ', 11 "are connected to appropriate light detecting means such as an optical power meter.

The waveguide 8 forms a thin film corresponding to a core or a clad of an optical fiber on a substrate and guides light, and includes (a) a ridge type, (b) a buried type, and
(c) It can be manufactured by a known type such as a loading type. For the production of waveguides, a method by epitaxial growth, CVD
And a method such as PVD, molecules, particle deposition, and ion doping. In the present invention, a method of doping the SiO ₂ thin film with GeO ₂ is practical. Optical fiber (array) connection bases 12 and 12 'are formed by inserting optical fibers into a substrate having grooves for optical fibers and attaching them with an adhesive such as a thermosetting resin or an ultraviolet curing resin. Is done.

The cooling means or heating means 3 is for cooling or heating the sample and the waveguide type sensor at the time of measurement within a predetermined temperature range in which a cloud point can be detected, and is attached in contact with the waveguide type sensor. Cooling means or heating means 3
Is, for example, a Peltier element placed on a heat sink,
It is a heat exchanger using a circulating refrigerant, a cryostat, or the like, and is preferably one known as a Peltier element. This is a II-VI compound semiconductor, namely Bi ₂ Te ₃ ,
It is composed of Sb ₂ Te ₃ , Bi ₂ Se ₃ and their solid solutions, connected to p-type and n-type semiconductors to which impurities are added, and is provided with a cooling unit and a heat radiating unit above and below. Such cooling means or heating means are commercially available under the trade name cleaning unit or thermomodule. FIG.
Here, the Peltier element 13 is shown as being arranged on a copper heat sink 14. An electrode cable 17 for supplying electricity to the semiconductor is connected. Such a cooling means or heating means is optimal for the purpose of the present invention in that it has no moving parts, is extremely small, and can perform local cooling with a simple configuration.
The combination of the waveguide structure used and a small local cooling or heating means such as a Peltier element can reduce the heat capacity of the device and increase the temperature and measurement control by using a substrate with good heat transfer. it can. For example, in a structure in which Peltier elements are assembled in two stages in a cascade, it is possible to control the temperature in the range of 30 to -15 ° C. required for the present invention. The upper surface of the cooling means or the heating means is placed in contact with the waveguide type sensor, and its lower surface is mounted on a heat sink such as a copper plate. However, it is also possible to use or use a cooling means or a heating means for cooling the entire waveguide type sensor by other means, for example, a heat exchanger using a circulating refrigerant or a cryostat utilizing adiabatic expansion generated when releasing a compressed gas. it can. A thermometer such as a thermocouple 16 is attached to a joint between the Peltier element 13 and the sensor substrate 5.

The concave shape of the liquid contact portion is preferably formed with a gentle curve rather than a shape in which dirt easily accumulates, such as a V-shape. FIG. 3 illustrates a case where this portion is formed as a part of a circle. The intersection of the input and output waveguides is represented by O, the center of the concave circle is represented by O ', the radius is represented by R, and the deviation between O and O' is represented by a parameter. The radius R of the concave circle of the liquid contact surface is about 0.5 to several millimeters as a size that can be easily processed. The incident end shape of the incident path is actually a part of an arc, whereas the actual waveguide core diameter is about 10 μm,
Since the radius R of the circle forming the concave surface of the liquid contact surface is as large as about 1 to several millimeters, the shape of the incident end may be approximated by the tangent of the concave circle at that portion. Light incident at theta ₁ angle to the entrance end of the entrance road is incident is refracted into the object to be measured liquid theta ₂ becomes an angle. Assuming that the refractive index of the waveguide core is n ₁ and the liquid refractive index is n ₂ , θ ₂ is n ₁ × sin θ ₁ = n
It is determined by ₂ × sin θ ₂ . At this time, if θ ₂ > θ ₁ , the refracted light enters and travels inside the intersection O of the output waveguide. As described above, when the light from the incident side waveguide enters the liquid, the light travels further toward the sensor head side (in other words, inside the concave portion) due to refraction, so that the sensor head front surface simply moves from the flat end face. As compared with the case where the light is emitted, the detection area is closer to the emission waveguide, so that the scattered light is more easily detected. In addition, only the temperature of the minute portion needs to be controlled, and the temperature controllability is also improved. It should be noted that θ ₁ is the critical angle θ _c obtained by θ _c = arcsin (n ₂ / n ₁ )
If it is larger than this, total reflection occurs at the incident end of the incident path, and light does not enter the liquid to be measured. Therefore, the waveguide refractive index, a / R, is such that total reflection does not occur in the liquid refractive index range near the cloud point.
Must be set to In designing the waveguides, the distances between the emission ends are set to be 10 μm or more so that adjacent emission paths are not mode-coupled to each other.

In this way, a cloud point meter is obtained which indicates the point at which the generation of precipitated fine particles occurs in a binary (on-off) system. By keeping the cloud point meter in contact with the petroleum and other chemicals to be measured and quickly controlling the temperature,
The cloud point can be detected continuously for each temperature cycle. Thus, a cloud point meter that is small and capable of high-speed response is obtained. In the conventional method, about 60 minutes were required for one measurement, but in the steady state of the sensor according to the present invention, it is greatly reduced to about 10 seconds, which enables extremely efficient measurement. In addition to light oil, similar measurements using the present invention can be performed for other petroleum products and many chemical products, and can also be used as a device for measuring fine particles in a liquid or a turbidity measuring device for a turbid liquid. . As a light source to be used, a visible to near-infrared laser having a normal output (several milliwatts or more) can detect scattered light without any problem.

[0017]

EXAMPLE A 20 μm thick SiO ₂ (refractive index: 1.458) as a clad and a 6 μm thick SiO ₂ .GeO ₂ (refractive index: 1.51) as a core were formed on a 1 mm thick silicon substrate by CVD. The film was formed to form a waveguide. A core pattern was formed by photolithography and reactive ion etching to produce a waveguide pattern having a thickness of 6 μm and a width of 6 μm. A cladding layer (thickness: 20 μm,
A refractive index of 1.458) was formed to obtain a buried waveguide. As the waveguide, one waveguide having an incident angle of 80 ° was provided as an incident path. One exit path is provided on the same side as the entrance path, one with an incident angle of 70 °, one in the direction perpendicular to the liquid contact surface, and across the concave section, 72 °, 75 °, 78
°, 81 °, 84 °, and 5 at 3 ° intervals. These are for entering scattered light from the rear, the measurement, and the front, respectively, and have a pattern of intersecting at the center O with a straight line as shown in FIG.

Pyrex sheet glass was adhered to the substrate on which the waveguide was formed with an ultraviolet-curing resin to form a reinforcing plate. The front and rear of this substrate (the connection surface between the liquid contact surface and the optical fiber) were cut by a dicing machine. At this time, the surface to be in contact with the liquid was cut so as to include the intersection O between the entrance path and the plurality of exit paths. As for the liquid contact surface, a / R = 0.75, where a is a shift between the intersection O of the incident and output waveguides and the center O ′ of the concave circle and R is the radius of the concave circle.
A liquid contact portion having a concave shape was formed. In this case, the incident angle θ ₁ to the incident end of the incident path is 47.6 °, and the critical angle for total reflection at this time is 83 ° at a refractive index of 1.50, 74 ° at 1.45, and
At 1.40, the angle is 68 °, which is larger than the incident angle at the incident end of the incident path, and the light enters the liquid as refracted light without being totally reflected at the incident end. This time, a red laser with a wavelength of 677 nm was used as a light source. This is because it is easy to observe the state of optical waveguide with the naked eye, it is easy to connect the sensor head to the optical fiber, and it is easy to observe the presence of scattered light at the cloud point. If used, a near-infrared laser may be used.

As for the connection surface with the optical fiber, the optical fiber was connected after optically polishing the end face of the waveguide. As the optical fiber, a single mode fiber was used for connecting the incident path, and a multimode fiber (core diameter 50 μm) was used for connecting the output path. These optical fibers were connected together in the form of an optical fiber array. An optical fiber array is formed by forming V-shaped grooves at the same pitch as the waveguide by cutting with a dicing machine or the like on a silicon or ceramic substrate, placing optical fibers therein, and bonding Pyrex glass as a reinforcing plate from above. Using. Attach a Peltier element to this waveguide sensor, and
Table 1 shows the results of measuring the cloud points of the four types of oils in a temperature range of up to -10 ° C.

[0020]

[Table 1]

The time from the room temperature to the cloud point is about 10 seconds. As a result of repeated measurement, it was confirmed that the measurement could be performed with an accuracy within ± 0.1 ° C.

[0022]

As described above, while the light is incident on the concave liquid contact portion from the incident path, the liquid contact portion is cooled or heated in a required temperature range, and the precipitated particles in the sample at the liquid contact portion are cooled. By detecting the scattered light of the incident light by a plurality of exit paths,
High-precision, high-speed cloud point measurement is possible.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the principle when applied to a petroleum product of the present invention. (a) is a state in which the petroleum product has not yet reached the cloud point and the incident light is transmitted through the petroleum product; (b)
FIG. 4 is an explanatory view showing a state where incident light is scattered due to generation of precipitated fine particles and the scattered light is output to an output fiber through an output path.

FIG. 2 is an exploded perspective view of an example of a cloud point meter according to the present invention.

FIG. 3 is an explanatory diagram in a case where a concave shape of a liquid contact part is formed as a part of a circle. (a) is an illustration of a reference numeral, and (b) is an explanatory diagram of details of an incident waveguide end.

[Explanation of symbols]

1: Cloud point meter 2: Optical waveguide sensor 3: Cooling or heating means 4: Detection surface 5: Substrate 6: Incident path 6a: Light incident end face from incident path to liquid 7: Exit path for backscattered light detection 7 ': Outgoing path for measuring scattered light detection 7 ": Outgoing path for backscattered light detection 7a: Light emitting end face from liquid to emission path 8: Waveguide 9: Waveguide layer 10: Incident optical fiber 11: Backscattered light Outgoing optical fiber for detection 11 ': Outgoing optical fiber for measuring scattered light 11 ": Outgoing optical fiber for detecting backscattered light 12: Connection base (optical fiber array) 13: Peltier element 14: Heat sink 15: Power cable 16: thermocouple O: input intersection O of the output waveguide shift of ': the center of the circle forming the concave R:: radius a of the circle forming the concave O and O' theta _1: light incident on the incident end of the incident path Angle θ ₂ : Angle of refraction of refracted light to measurement object

Continuation of the front page (56) References JP-A-58-7550 (JP, A) JP-A-61-17941 (JP, A) JP-A-6-109629 (JP, A) JP-A-2-50673 (JP) , U) Jikken Sho 53-12232 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 25/00-25/72 G01N 21/47

Claims (4)

(57) [Claims] 1. A sample to be measured is cooled or heated in a predetermined temperature range while light is incident on the sample to be measured from an incident path, and forward scattered light of incident light due to precipitation of a precipitate in the sample to be measured is output. A cloud point is measured by detecting a cloud point, and the incident path and the output path are waveguides having a waveguide structure on a substrate. 2. An apparatus according to claim 1, further comprising an incident path for entering light into a detection area in contact with the sample to be measured, and a plurality of exit paths for detecting forward scattered light from the detection area, wherein the entrance path and the exit path are substrates. A cloud point meter, which is a waveguide having an upper waveguide structure and provided with a cooling means or a heating means in contact with the waveguide. 3. The cloud point meter according to claim 2, wherein the detection area has a concave shape. 4. A cloud point meter according to claim 2, wherein said cooling means or heating means is a Peltier element mounted on a heat sink, a heat exchanger using a circulating refrigerant, or a cryostat.