Patent Description:
The present disclosure relates to a calibration curve generation method.

<CIT>, hereinafter PTL <NUM> describes a technique of analyzing components of LNG using a gas chromatograph in an LNG production process. The "LNG" stands for liquefied natural gas.

<NPL>, discloses a cryostat cell for liquefying alkanes and liquid natural gas and recording NIR spectra through windows in the cryostat, and suggests chemometrics for analyzing LNG. Additionally, <CIT> and <CIT> form part of the state of the art relative to the present disclosure.

To analyze components of LNG using a gas chromatograph, the LNG needs to be vaporized. Thus, it takes time to vaporize the LNG for analysis.

In view of this, a near-infrared spectrometer may be used to, without vaporizing liquefied gas such as LNG, analyze properties of liquefied gas such as the concentration of each component. Near-infrared light which is light of <NUM> to <NUM> in wavelength resonates with vibration and rotation of molecules and is absorbed. Wavelength subjected to absorption differs depending on the chemical structure of a molecule, and accordingly information about the chemical structure of a substance can be obtained from an absorbance spectrum. A near-infrared spectrometer irradiates a sample with near-infrared light. The sample absorbs light of specific wavelength, as a result of which an absorbance spectrum is obtained. The composition can be determined from the absorbance spectrum using a calibration curve. Since the sample is merely irradiated with near-infrared light, high-speed analysis is possible without destroying the sample. The calibration curve is a formula representing the relationship between the property value and the absorbance spectrum of the liquefied gas, or data indicating the formula.

However, to analyze the property of the liquefied gas using the near-infrared spectrometer, the calibration curve needs to be generated beforehand. The generation of the calibration curve in an actual process requires collecting a sufficient amount of spectrum data over a long period of time until the property value of the liquefied gas varies so as to cover a desired range. Thus, it takes time to enable the analysis.

An object of the present disclosure is to improve the efficiency of liquefied gas property analysis.

Herein disclosed is a calibration curve generation system. With such a system, spectrum data can be collected without installing a near-infrared measuring instrument in an actual process. By using, as the sample gas, a plurality of samples each adjusted so that the concentration of each component covers a desired range, a sufficient amount of spectrum data can be collected in a short time. Moreover, the range of the concentration of each component can be freely widened. From the collected spectrum data, a calibration curve representing the relationship between the concentration of each componentand the absorbance spectrum of liquefied gas can be generated. Thus, by use of the system including the near-infrared measuring instrument, the concentration of each componentof the liquefied gas can be analyzed without vaporizing the liquefied gas. This improves the efficiency of liquefied gas property analysis.

In one embodiment, the liquefaction mechanism may include: a cylindrical body configured to form a liquefaction chamber into which the sample gas is to be introduced, in the container; and a cooling instrument configured to cool the cylindrical body to liquefy the sample gas in the liquefaction chamber, part of the near-infrared probe may be located in the liquefaction chamber, and the near-infrared measuring instrument may be configured to irradiate the sample gas in the liquefaction chamber in a state of being liquefied by the cooling instrument with near-infrared light via the near-infrared probe, and detect at least one of transmitted light or reflected light via the near-infrared probe to measure the absorbance spectrum of the sample gas. According to this embodiment, the sample gas is liquefied in the liquefaction chamber, and the sample gas in a liquefied state is irradiated with near-infrared light for measurement in the same liquefaction chamber. In this way, the absorbance spectrum of the sample gas in a liquefied state can be measured with high accuracy.

In one embodiment, the liquefaction mechanism may further include: a heat transfer material configured to thermally connect the cooling instrument to the cylindrical body; a heater configured to heat the heat transfer material; and a temperature regulator configured to regulate a temperature of the heat transfer material by controlling the heater. According to this embodiment, both cooling and heating are possible, so that the temperature in the liquefaction chamber can be freely regulated.

In one embodiment, the cooling instrument may include: a coolant tank into which a coolant is to be injected; and a cooling pipe configured to convey the coolant from the coolant tank to the heat transfer material. According to this embodiment, the temperature in the liquefaction chamber can be decreased with a simple structure.

In one embodiment, the liquefaction mechanism may further include: a heat transfer material configured to thermally connect the cooling instrument to the near-infrared probe; a heater configured to heat the heat transfer material; and a temperature regulator configured to regulate a temperature of the heat transfer material by controlling the heater. According to this embodiment, both cooling and heating are possible, so that the temperature in the liquefaction chamber can be freely regulated.

In one implementation, the cooling instrument may include a coolant tank into which a coolant is to be injected, and the heat transfer material may be configured to thermally connect an outer shell of the coolant tank to the near-infrared probe. According to this embodiment, the temperature in the liquefaction chamber can be decreased with a simple structure.

In one implementation, the liquefaction mechanism may further include an introduction tube having an inner diameter of <NUM> or less and configured to introduce the sample gas into the liquefaction chamber. According to this embodiment, the introduction tube is narrow, which prevents backflow of the sample gas.

In one implementation, a temperature sensor is located in the liquefaction chamber and configured to measure a temperature of the sample gas. According to this embodiment, the temperature of the sample gas in a liquefied state can be measured with high accuracy.

The calibration curve generation system includes configured to analyze correlations between the measurement results of the absorbance spectrum of each sample of the plurality of samples, being injected as the sample gas, obtained by the measurement device and the concentration of the components included in each sample thereby to generate a calibration curve relating an absorbance spectrum of a liquified sample gas and the concentration of each of the components in the sample gas. With such a calibration curve generation system, by using, as the sample gas, a plurality of samples each adjusted so that the concentration of each component covers a desired range, a highly versatile calibration curve, namely, a universal calibration curve, can be generated in a short time. Moreover, the range of the concentration of each component can be freely widened. When analyzing liquefied gas using an analysis device including a near-infrared measuring instrument, the concentration of each component of the liquefied gas can be obtained by applying the measurement result of the absorbance spectrum of the liquefied gas obtained by the near-infrared measuring instrument to the generated calibration curve. This improves the efficiency of liquefied gas property analysis.

The generation device may be configured to generate, from a measurement result of the absorbance spectrum of the sample gas obtained for each combination of a concentration of each component and the temperature as a result of using a plurality of samples that differ in property value as the sample gas and changing the temperature of the sample gas in the liquefaction chamber, a calibration curve representing a relationship among the concentration of each component, the temperature, and the absorbance spectrum of the sample gas. Accordingly, an offset in the spectrum measurement result caused by a temperature difference can be corrected.

Such a calibration curve generation system as disclosed herein can be used to implement the present invention. According to the present invention, there is provided a calibration curve generation method as recited in claim <NUM> below. With such a method, spectrum data can be collected without installing a near-infrared measuring instrument in an actual process. By using, as the sample gas, a plurality of samples each adjusted so that the concentration of each component covers a desired range, a sufficient amount of spectrum data can be collected in a short time. Moreover, the range of the property value can be freely widened. From the collected spectrum data, a calibration curve representing the relationship between the concentration of each componentand the absorbance spectrum of liquefied gas can be generated. Thus, by use of the measurement device including the near-infrared measuring instrument, the property of the liquefied gas can be analyzed without vaporizing the liquefied gas. This improves the efficiency of liquefied gas property analysis.

In one embodiment, the method may include: filling a buffer tank with the sample gas after vacuuming the buffer tank; and injecting the sample gas from the buffer tank into the container. According to this embodiment, the purity of the sample gas can be maintained.

The calibration curve generation method includes generating, from a measurement result of the absorbance spectrum of the sample gas obtained for each concentration of each componentas a result of using a plurality of samples that differ in concentration of each component as the sample gas, a calibration curve representing a relationship between the concentration of each component and the absorbance spectrum of the sample gas. With such a calibration curve generation method, by using, as the sample gas, a plurality of samples each adjusted so that the concentration of each component covers a desired range, a highly versatile calibration curve, namely, a universal calibration curve, can be generated in a short time. Moreover, the range of the property value can be freely widened. When analyzing the concentration of each component of liquefied gas using an analysis device including a near-infrared measuring instrument, the concentration of each component of the liquefied gas can be obtained by applying the measurement result of the absorbance spectrum of the liquefied gas obtained by the near-infrared measuring instrument to the generated calibration curve. This improves the efficiency of liquefied gas property analysis.

The calibration curve generation method may include: measuring a temperature of the sample gas in the liquefied state and generating, from a measurement result of the absorbance spectrum of the sample gas obtained for each combination of the concentration of each component and the temperature as a result of using a plurality of samples that differ in concentration of each component as the sample gas and changing the temperature of the sample gas in the liquefied state, a calibration curve representing a relationship among the concentration of each component, the temperature, and the absorbance spectrum of the sample gas. Accordingly, an offset in the spectrum measurement result caused by a temperature difference can be corrected.

In one embodiment, the analysis device may further include an input interface configured to receive input of a measurement result of a temperature of the liquefied gas, wherein the memory is configured to store, as the calibration curve, a calibration curve representing a relationship among the concentration of each component, a temperature, and the absorbance spectrum of the sample gas, the calibration curve being generated from a measurement result of the absorbance spectrum of the sample gas obtained for each combination of the concentration of each componentand the temperature as a result of measuring the temperature of the sample gas in the liquefied state, using the plurality of samples that differ in concentration of each componentas the sample gas, and changing the temperature of the sample gas in the liquefied state, and the controller is configured to calculate the concentration of each componentof the liquefied gas, from the calibration curve stored in the memory, the measurement result of the temperature of the liquefied gas input in the input interface, and the measurement result of the absorbance spectrum of the liquefied gas obtained by the meter. According to this embodiment, an offset in the spectrum measurement result caused by a temperature difference can be corrected.

The invention may be applied in a liquefied gas production plant. With such a liquefied gas production plant, the property of the liquefied gas can be analyzed without vaporizing the liquefied gas. This improves the efficiency of liquefied gas property analysis.

The invention may be applied in an analysis method. With such an analysis method, the concentration of each componentof the liquefied gas can be analyzed without vaporizing the liquefied gas. This improves the efficiency of liquefied gas property analysis.

In one embodiment, the method may include: measuring a temperature of the liquefied gas; and calculating the concentration of each component value of the liquefied gas from, as the calibration curve, a calibration curve representing a relationship among the property value, a temperature, and the absorbance spectrum of the sample gas and the measurement result of the absorbance spectrum of the liquefied gas and a measurement result of the temperature of the liquefied gas, the calibration curve being generated from the measurement result of the absorbance spectrum of the sample gas obtained for each combination of the concentration of each component value and the temperature as a result of measuring the temperature of the sample gas in the liquefied state, using the plurality of samples that differ in concentration of each component value as the sample gas, and changing the temperature of the sample gas in the liquefied state. According to this embodiment, an offset in the spectrum measurement result caused by a temperature difference can be corrected.

According to the present disclosure, it is possible to improve the efficiency of liquefied gas property analysis.

A property value of LNG may be measured directly and continuously by using a near-infrared spectrometer, without vaporizing the LNG. This measurement can be performed by applying, to a calibration curve generated beforehand, spectrum data which is information of absorbance obtained from at least one of transmitted light or reflected light (i.e. transmitted light and/or reflected light) of the LNG to be measured.

To clarify problems regarding the generation of a calibration curve, a comparative example will be described below with reference to <FIG>, prior to the description of one of the disclosed embodiments.

In the drawing, "NIR" stands for near infrared.

In this comparative example, a calibration curve <NUM> is generated by introducing a near-infrared (NIR) measuring instrument <NUM> into a facility in which LNG is actually used. The LNG to be analyzed flows in a process line <NUM>.

A calibration curve generation system <NUM> according to this comparative example includes a near-infrared (NIR) probe <NUM>, the near-infrared measuring instrument <NUM>, a gas chromatograph (GC) <NUM>, and a computer installed with a chemometrics program <NUM>.

The near-infrared probe <NUM> is inserted in piping of the process line <NUM>. The near-infrared measuring instrument <NUM> is connected to the near-infrared probe <NUM>. The near-infrared measuring instrument <NUM> measures the absorbance of near-infrared light by the LNG, and outputs spectrum data <NUM>. The gas chromatograph <NUM> is an analyzer for analyzing a property value of the LNG corresponding to the spectrum data <NUM> output from the near-infrared measuring instrument <NUM>. The gas chromatograph <NUM> vaporizes the LNG, analyzes the components of the LNG, and outputs property data <NUM>.

The near-infrared measuring instrument <NUM> continuously detects the spectrum in a cycle of <NUM> seconds or less, and outputs the detection result as the spectrum data <NUM>. The gas chromatograph <NUM> detects the components of the LNG in a cycle of about <NUM> minutes to <NUM> minutes, calculates the concentration of each measured component from the detection result and calculates the calorific value or density of the LNG from the concentration, and outputs the calculation result as the property data <NUM>. The calibration curve generation system <NUM> calculates the correlation between the spectrum data <NUM> output from the near-infrared measuring instrument <NUM> and the property data <NUM> output from the gas chromatograph <NUM> using the chemometrics program <NUM>, to generate the calibration curve <NUM>. Once the generated calibration curve <NUM> is installed into a near-infrared spectrometer, the near-infrared spectrometer can be used to measure the property value of the LNG without vaporizing the LNG.

For the generation of the calibration curve <NUM>, the number of pieces of spectrum data <NUM> needs to be sufficient to cover a range in which each factor that varies the spectrum, such as the concentration of each measured component and the temperature, can vary. For example, in the case where three factors each change in three ways, the number of pieces of spectrum data <NUM> necessary to generate the calibration curve <NUM> to measure these factors is <NUM> × <NUM> × <NUM> = <NUM>. In the case of directly measuring the LNG flowing in the process line <NUM>, examples of factors that vary the spectrum include the concentration of each component such as methane, ethane, propane, butane, isobutane, and nitrogen, the temperature, the pressure, and the density.

With a method of directly measuring the LNG flowing in the process line <NUM>, it is necessary to introduce the near-infrared measuring instrument <NUM> into an actual process and collect data of about six months, in order to obtain data for generating the calibration curve <NUM>. The composition of LNG differs depending on the producing country, and also varies depending on the manner of storage in the plant and the process. LNG does not form a liquid unless the temperature is low or unless the temperature is low and the pressure is higher than atmospheric pressure. Therefore, it is difficult to prepare LNG of any composition in such an amount that can be handled in a laboratory.

With the foregoing method, it takes much time and labor to enable the measurement of the property value, and only a calibration curve <NUM> of a limited range for each process can be generated. While the composition of LNG differs depending on the producing region, the concentration range of methane is approximately <NUM> % to <NUM> %. On the other hand, the concentration range of methane in a calibration curve <NUM> generated in a process was approximately <NUM> % to <NUM> %. This is because, given the composition of LNG as raw material and the operation in the actual process, the concentration only varied in such a range in six months. Since each property value outside the range of the generated calibration curve <NUM> cannot be measured, in the case where the concentration range to be measured changes, the calibration curve <NUM> needs to be regenerated or renewed. Even when it is known that the range changes in the future, the calibration curve <NUM> that covers the new range cannot be generated without the spectrum in the actual process.

Therefore, the following points can be problematic in the comparative example.

One of the disclosed embodiments will be described below, with reference to the drawings. The problems stated above can be solved according to this embodiment.

In the drawings, the same or corresponding parts are given the same reference signs. In the description of this embodiment, the description of the same or corresponding parts is omitted or simplified as appropriate.

An overview of a calibration curve generation system <NUM> according to this embodiment will be described below, with reference to <FIG> and <FIG>.

The calibration curve generation system <NUM> performs the following steps:.

By using, as the sample gas, a plurality of samples that differ in property value, the measurement result of the absorbance spectrum of the sample gas is obtained for each property value as a result of these steps.

The calibration curve generation system <NUM> further performs the following step:
<NUM>. From the measurement result of the absorbance spectrum of the sample gas obtained for each property value, a calibration curve <NUM> representing the relationship between the property value and the absorbance spectrum of the sample gas is generated.

In this embodiment, the sample gas is not natural LNG, but gas resembling LNG. Specifically, the sample gas is gas produced so as to cover an assumed concentration range of each component of LNG. The sample gas may be gas resembling any other type of liquefied gas such as LPG or vinyl chloride. The "LPG" stands for liquefied petroleum gas.

In this embodiment, the calibration curve generation system <NUM> liquefies the sample gas resembling LNG, measures the absorbance spectrum, and generates a universal calibration curve for LNG direct measurement covering assumed variable factors of LNG. That is, the calibration curve generation system <NUM> generates the calibration curve <NUM> that covers the composition distribution of LNG. As a result of generating such a calibration curve <NUM>, the property value of LNG can be continuously analyzed without performing calibration curve generation on site.

For the generation of the calibration curve <NUM>, the number of pieces of spectrum data <NUM> needs to be sufficient to cover a range in which each factor that varies the absorbance spectrum, such as the concentration of each measured component and the temperature, can vary, as mentioned earlier. Accordingly, the calibration curve generation system <NUM> liquefies the sample gas of any concentration, measures the absorbance of the liquefied sample gas for near-infrared light, and acquires spectrum data <NUM>.

The structure of the calibration curve generation system <NUM> will be described below.

The calibration curve generation system <NUM> includes a measurement device <NUM> and a generation device <NUM>.

The measurement device <NUM> includes the container <NUM>, a liquefaction mechanism <NUM>, the near-infrared probe <NUM>, and the near-infrared measuring instrument <NUM>.

The sample gas is injected into the container <NUM>. The liquefaction mechanism <NUM> is a mechanism that liquefies the sample gas in the container <NUM>. The near-infrared probe <NUM> is installed to extend from inside to outside the container <NUM>. The near-infrared measuring instrument <NUM> is a device that measures the absorbance spectrum of the sample gas in a state of being liquefied by the liquefaction mechanism <NUM>, via the near-infrared probe <NUM>.

The liquefaction mechanism <NUM> includes a cylindrical body <NUM> and a cooling instrument <NUM>.

The cylindrical body <NUM> is a part that forms a liquefaction chamber <NUM> in the container <NUM>. The cylindrical body <NUM> may have any shape such as a cylinder or a square tube, as long as it is hollow. In this embodiment, the cylindrical body <NUM> is made of copper. The liquefaction chamber <NUM> is a space into which the sample gas is introduced. The cooling instrument <NUM> is a device that cools the cylindrical body <NUM> to liquefy the sample gas in the liquefaction chamber <NUM>. Part of the near-infrared probe <NUM> is located in the liquefaction chamber <NUM>. The near-infrared measuring instrument <NUM> irradiates the sample gas in the liquefaction chamber <NUM> in a state of being liquefied by the cooling instrument <NUM> with near-infrared light via the near-infrared probe <NUM>, and detects at least one of transmitted light or reflected light via the near-infrared probe <NUM> to measure the absorbance spectrum of the sample gas. In this embodiment, the near-infrared probe <NUM> is provided with a pair of light guides <NUM> and a mirror <NUM>. Near-infrared light emitted from the near-infrared measuring instrument <NUM> reaches the inside of the liquefaction chamber <NUM> through one light guide <NUM>. Light that has passed through the sample gas in a liquefied state in the liquefaction chamber <NUM> reflects off the mirror <NUM>, and returns to the near-infrared measuring instrument <NUM> through the other light guide <NUM>.

The liquefaction mechanism <NUM> further includes a first heat transfer material <NUM>, a first heater <NUM>, and a first temperature regulator <NUM>. In this embodiment, the liquefaction mechanism <NUM> further includes a first temperature sensor <NUM>.

The first heat transfer material <NUM> is a heat transfer material that thermally connects the cooling instrument <NUM> to the cylindrical body <NUM>. In this embodiment, the first heat transfer material <NUM> is a heat exchanger plate made of copper. The first heater <NUM> is a heater that heats the first heat transfer material <NUM>. The first heater <NUM> is attached to the first heat transfer material <NUM>. The first temperature regulator <NUM> is a temperature regulator that regulates the temperature of the first heat transfer material <NUM> by controlling the first heater <NUM>. The first temperature sensor <NUM> is a sensor that measures the temperature of the first heater <NUM>. The first temperature sensor <NUM> is attached to a part of the first heat transfer material <NUM> adjacent to the first heater <NUM>. The first temperature sensor <NUM> may measure the temperature of the first heat transfer material <NUM>.

The cooling instrument <NUM> includes a coolant tank <NUM> and a cooling pipe <NUM>. In this embodiment, the cooling instrument <NUM> further includes a temperature regulation part <NUM>.

The coolant tank <NUM> is made of steel in this embodiment. Specifically, the coolant tank <NUM> is made of stainless steel. A coolant is injected into the coolant tank <NUM>. The coolant may be any refrigerant. In this embodiment, the coolant is liquid nitrogen. The coolant tank <NUM> is located in the container <NUM>. The coolant tank <NUM> is provided with an inlet tube <NUM> and an outlet tube <NUM>. The inlet tube <NUM> and the outlet tube <NUM> both pass through the ceiling of the coolant tank <NUM> and the canopy of the container <NUM>. One end of each of the inlet tube <NUM> and the outlet tube <NUM><NUM> is open so as to communicate with the internal space of the coolant tank <NUM>. The other end of each of the inlet tube <NUM> and the outlet tube <NUM> is open so as to communicate with the external space of the container <NUM>. Liquid nitrogen is injected into the coolant tank <NUM> from outside the container <NUM> through the inlet tube <NUM>. Liquid nitrogen that has evaporated in the coolant tank <NUM> is discharged to outside the container <NUM> through the outlet tube <NUM>. The first heat transfer material <NUM> is located below and away from the coolant tank <NUM>. The cooling pipe <NUM> is a pipe that conveys the coolant which is liquid nitrogen from the coolant tank <NUM> to the first heat transfer material <NUM>. The cooling pipe <NUM> extends from the ceiling of the coolant tank <NUM> to the bottom of the coolant tank <NUM>, and passes through the bottom of the coolant tank <NUM> and further extends downward to come into contact with the first heat transfer material <NUM>. The cooling pipe <NUM> is made of steel and specifically made of stainless steel in this embodiment, as with the coolant tank <NUM>. The cooling pipe <NUM> has a hole <NUM> through which the internal space of the coolant tank <NUM> and the internal space of the cooling pipe <NUM> communicate with each other, at a position slightly higher than the bottom of the coolant tank <NUM>. A cooler <NUM> is formed in the cooling pipe <NUM> at one end closer to the first heat transfer material <NUM>. The temperature regulation part <NUM> is placed in the cooling pipe <NUM> so as to be displaceable along the extending direction of the cooling pipe <NUM>. In this embodiment, the temperature regulation part <NUM> is made of a porous material, and allows liquid nitrogen to permeate and exude slowly. A knob <NUM> for adjusting the position of the temperature regulation part <NUM> is attached to the temperature regulation part <NUM> via a long material <NUM>.

The liquefaction mechanism <NUM> further includes a second heat transfer material <NUM>, a second heater <NUM>, and a second temperature regulator <NUM>. In this embodiment, the liquefaction mechanism <NUM> further includes a second temperature sensor <NUM>.

The second heat transfer material <NUM> is a heat transfer material that thermally connects the cooling instrument <NUM> to the near-infrared probe <NUM>. In this embodiment, the second heat transfer material <NUM> is a thermal anchor made of copper. The second heater <NUM> is a heater that heats the second heat transfer material <NUM>. The second heater <NUM> is attached to the second heat transfer material <NUM>. The second temperature regulator <NUM> is a temperature regulator that regulates the temperature of the second heat transfer material <NUM> by controlling the second heater <NUM>. The second temperature sensor <NUM> is a sensor that measures the temperature of the second heater <NUM>. The second temperature sensor <NUM> is attached to a part of the second heat transfer material <NUM> adjacent to the second heater <NUM>. The second temperature sensor <NUM> may measure the temperature of the second heat transfer material <NUM>.

The second heat transfer material <NUM> thermally connects the outer shell of the coolant tank <NUM> to the near-infrared probe <NUM>.

The liquefaction mechanism <NUM> further includes an introduction tube <NUM>. In this embodiment, the liquefaction mechanism <NUM> further includes a third heater <NUM>, a third temperature regulator <NUM>, and a third temperature sensor <NUM>.

The introduction tube <NUM> is piping that introduces the sample gas into the liquefaction chamber <NUM>. In this embodiment, the inner diameter of the introduction tube <NUM> is <NUM> or less, and specifically <NUM>. The third heater <NUM> is a heater that heats the introduction tube <NUM>. The third heater <NUM> is attached to a part of the introduction tube <NUM> close to an introduction port into the liquefaction chamber <NUM>. The third temperature regulator <NUM> is a temperature regulator that regulates the temperature of the introduction tube <NUM> by controlling the third heater <NUM>. The third temperature sensor <NUM> is a sensor that measures the temperature of the third heater <NUM>. The third temperature sensor <NUM> is attached to a part of the introduction tube <NUM> adjacent to the third heater <NUM>. The third temperature sensor <NUM> may measure the temperature of the introduction tube <NUM>.

The introduction tube <NUM> is connected to a buffer tank <NUM> via an on-off valve 103a. The buffer tank <NUM> is connected to a sample gas cylinder <NUM> via an on-off valve 104a. Sample gas prepared according to any composition is enclosed in the sample gas cylinder <NUM>. The introduction tube <NUM> is also connected to a vacuum pump (not illustrated). The vacuum pump is capable of creating a high vacuum in the introduction tube <NUM>, and capable of creating a high vacuum in the buffer tank <NUM>. The introduction tube <NUM> is further connected to a pressure gauge <NUM>. The buffer tank <NUM> is connected to a pressure gauge 103b. The pressure gauge <NUM> and the pressure gauge 103b can respectively measure the pressure in the introduction tube <NUM> and the pressure in the buffer tank <NUM> in a state in which the on-off valve 103a and the on-off valve 104a are closed. The calibration curve generation system <NUM> can maintain the pressure in the introduction tube <NUM> at any pressure based on the measurement result of the pressure gauge <NUM>, and maintain the pressure in the buffer tank <NUM> at any pressure based on the measurement result of the pressure gauge 103b.

The measurement device <NUM> further includes a temperature sensor <NUM>.

The temperature sensor <NUM> is located in the liquefaction chamber <NUM>. The temperature sensor <NUM> is a sensor that measures the temperature in the liquefaction chamber <NUM>, i.e. the temperature of the sample gas injected in the liquefaction chamber <NUM> and the liquefied sample gas.

In the measurement device <NUM>, the container <NUM> and the liquefaction mechanism <NUM> constitute a cryostat <NUM>. The cryostat <NUM> is a device that cools the sample using liquid nitrogen. The cryostat <NUM> is produced to be capable of controlling the liquefaction chamber <NUM> in a range of -<NUM> to <NUM>.

The operation of the measurement device <NUM> will be described below.

The measurement device <NUM> performs the following steps as steps of a spectrum measurement method and a calibration curve generation method according to this embodiment:.

In the case where the sample gas contains butane, given that butane has a low melting point of -<NUM>, the temperature of the introduction tube <NUM> may be regulated by controlling the third heater <NUM> of the introduction tube <NUM> by the third temperature regulator <NUM> to prevent freezing of the introduction tube <NUM>. In such a case, the third temperature regulator <NUM> performs PID control depending on the temperature measurement value obtained by the third temperature sensor <NUM>.

The generation device <NUM> stores property data <NUM> indicating the property value of the sample gas beforehand. The property data <NUM> indicates the composition of the sample gas enclosed in the sample gas cylinder <NUM>, which is known when preparing the sample gas. The generation device <NUM> is installed with a chemometrics program <NUM>.

The operation of the generation device <NUM> will be described below.

The generation device <NUM> performs the following step as a step of the calibration curve generation method according to this embodiment:
<NUM>. The calibration curve <NUM> is generated using the chemometrics program <NUM>, from the property value of the sample gas indicated by the property data <NUM>, the spectrum measured using the near-infrared measuring instrument <NUM>, and the temperature data in the spectrum measurement measured using the temperature sensor <NUM>.

The detailed structure of the generation device <NUM> will be described below, with reference to <FIG>.

The generation device <NUM> includes a controller <NUM>, a memory <NUM>, a communication interface <NUM>, an input interface <NUM>, and an output interface <NUM>.

The controller <NUM> is one or more processors. Examples of processors that can be used include general-purpose processors such as CPU and dedicated processors specialized in specific processing. The "CPU" stands for central processing unit. The controller <NUM> may include one or more dedicated circuits, or one or more processors may be replaced with one or more dedicated circuits in the controller <NUM>. Examples of dedicated circuits that can be used include FPGA and ASIC. The "FPGA" stands for field-programmable gate array. The "ASIC" stands for application specific integrated circuit. The controller <NUM> executes information processing relating to the operation of the generation device <NUM> while controlling each component in the generation device <NUM>.

The memory <NUM> is one or more memories. Examples of memories that can be used include semiconductor memory, magnetic memory, and optical memory. The memory may function as a main storage device, an auxiliary storage device, or cache memory. The memory <NUM> stores information used for the operation of the generation device <NUM> and information obtained as a result of the operation of the generation device <NUM>.

The communication interface <NUM> is one or more communication modules. Examples of communication modules that can be used include communication modules conforming to LAN standards. The "LAN" stands for local area network. The communication interface <NUM> receives information used for the operation of the generation device <NUM>, and transmits information obtained as a result of the operation of the generation device <NUM>.

The input interface <NUM> is one or more input interfaces. Examples of input interfaces that can be used include physical keys, capacitive keys, pointing devices, and touch screens provided integrally with displays. The input interface <NUM> receives input of information used for the operation of the generation device <NUM>, from a user.

The output interface <NUM> is one or more output interfaces. Examples of output interfaces that can be used include displays. Examples of displays that can be used include LCDs and organic EL displays. The "LCD" stands for liquid crystal display. The "EL" stands for electro luminescence. The output interface <NUM> outputs information obtained as a result of the operation of the generation device <NUM>, to the user.

The functions of the generation device <NUM> are implemented by the processor included in the controller <NUM> executing a calibration curve generation program according to this embodiment including the chemometrics program <NUM>. That is, the functions of the generation device <NUM> are implemented by software. The calibration curve generation program is a program for causing a computer to execute the processes of the steps included in the operation of the generation device <NUM> to achieve the functions corresponding to the processes of the steps. In other words, the calibration curve generation program is a program for causing the computer to function as the generation device <NUM>.

The program can be recorded in a computer-readable recording medium. Examples of computer-readable recording media that can be used include magnetic recording devices, optical discs, magnetooptical recording media, and semiconductor memory. The program is distributed, for example, by selling, giving, or renting a portable recording medium such as DVD or CD-ROM in which the program is recorded. The "DVD" stands for digital versatile disc. The "CD-ROM" stands for compact disc read only memory. The program may be distributed by storing the program in a storage of a server and transferring the program from the server to another computer via a network. The program may be provided as a program product.

For example, the computer stores the program recorded in the portable recording medium or the program transferred from the server, in memory. The computer then reads the program stored in the memory by a processor, and executes processes according to the read program by the processor. The computer may directly read the program from the portable recording medium and execute processes according to the program. The computer may, each time the program is transferred from the server to the computer, execute processes according to the received program. Processes may be executed by an ASP-type service that achieves functions only by execution instruction and result acquisition, without transferring the program from the server to the computer. The "ASP" stands for application service provider. The program includes information that is to be processed by an electronic computer equivalent to a computer program. For example, data that is not a direct command to a computer but has property of defining a computer process is "equivalent to a computer program".

All or part of the functions of the generation device <NUM> may be implemented by the dedicated circuit included in the controller <NUM>. That is, all or part of the functions of the generation device <NUM> may be implemented by hardware.

The detailed operation of the generation device <NUM> will be described below, with reference to <FIG>. The flowchart in <FIG> illustrates the procedure of the calibration curve generation program according to this embodiment.

In step S11, the controller <NUM> acquires, via the communication interface <NUM> or the input interface <NUM>, the spectrum data <NUM> indicating the measurement result of the absorbance spectrum of the sample gas obtained by the measurement device <NUM> for each property value as a result of using, as the sample gas, a plurality of samples that differ in property value. The controller <NUM> stores the acquired spectrum data <NUM> in the memory <NUM>. The property data <NUM> indicating the property value of each sample is stored in the memory <NUM> beforehand.

In this embodiment, the spectrum data <NUM> is data indicating the measurement result of the absorbance spectrum of the sample gas obtained by the measurement device <NUM> for each combination of property value and temperature as a result of using, as the sample gas, a plurality of samples that differ in property value and changing the temperature of the sample gas in the liquefaction chamber <NUM>.

In step S12, the controller <NUM> generates the calibration curve <NUM> representing the relationship between the property value and the absorbance spectrum of the sample gas, from the measurement result of the absorbance spectrum of the sample gas indicated by the spectrum data <NUM> stored in the memory <NUM> in step S11. Specifically, the calibration curve <NUM> is data indicating a formula that includes a parameter for inputting the absorbance spectrum of LNG and outputs the concentration of each component of the LNG or the calorific value or density of the LNG corresponding to the input value of the absorbance spectrum.

Specifically, the controller <NUM> reads the spectrum data <NUM> and the property data <NUM> from the memory <NUM>. The controller <NUM> executes the chemometrics program <NUM> to analyze the correlation between the measurement value of the absorbance spectrum of each sample indicated by the spectrum data <NUM> and the concentration of each component of each sample or the calorific value or density of each sample indicated by the property data <NUM>, thus generating the calibration curve <NUM>.

In this embodiment, the controller <NUM> generates, from the measurement result of the absorbance spectrum of the sample gas indicated by the spectrum data <NUM>, the calibration curve <NUM> representing the relationship among the property value, the temperature, and the absorbance spectrum of the sample gas. Specifically, the calibration curve <NUM> is data indicating a formula that includes a parameter for inputting the temperature of LNG and a parameter for inputting the absorbance spectrum of the LNG and outputs the concentration of each component of the LNG or the calorific value or density of the LNG corresponding to the input values of the temperature and absorbance spectrum.

In step S13, the controller <NUM> outputs the calibration curve <NUM> generated in step S12, via the communication interface <NUM> or the output interface <NUM>.

An overview of a property analysis system <NUM> according to this embodiment will be described below, with reference to <FIG>.

The property analysis system <NUM> performs the following steps as steps of a property analysis method according to this embodiment:.

In this embodiment, the liquefied gas is LNG. In the case where the sample gas used in the calibration curve generation system <NUM> is gas resembling LPG, the liquefied gas is LPG. In the case where the sample gas used in the calibration curve generation system <NUM> is gas resembling vinyl chloride, the liquefied gas is vinyl chloride.

The structure of the property analysis system <NUM> will be described below.

The property analysis system <NUM> includes a near-infrared (NIR) probe <NUM> and an analysis device <NUM> including a near-infrared (NIR) measuring instrument.

The near-infrared probe <NUM> is inserted in piping of a process line <NUM> in an LNG production plant. The analysis device <NUM> is a near-infrared spectrometer to which the calibration curve <NUM> is applied. The analysis device <NUM> is connected to the near-infrared probe <NUM>. The analysis device <NUM> measures the absorbance spectrum of the LNG flowing in the process line <NUM>, to obtain spectrum data <NUM>. The analysis device <NUM> applies the obtained spectrum data <NUM> to the calibration curve <NUM> generated by the calibration curve generation system <NUM> beforehand, to determine a property value <NUM> of the LNG.

The property analysis system <NUM> further includes a temperature sensor <NUM>.

The temperature sensor <NUM> is located in the piping of the process line <NUM>. The temperature sensor <NUM> is a sensor that measures the temperature of the LNG flowing in the process line <NUM>.

The detailed structure of the analysis device <NUM> will be described below, with reference to <FIG>.

The analysis device <NUM> includes a controller <NUM>, a memory <NUM>, a communication interface <NUM>, an input interface <NUM>, an output interface <NUM>, and a meter <NUM>.

The controller <NUM> is one or more processors. Examples of processors that can be used include general-purpose processors such as CPU and dedicated processors specialized in specific processing. The controller <NUM> may include one or more dedicated circuits, or one or more processors may be replaced with one or more dedicated circuits in the controller <NUM>. Examples of dedicated circuits that can be used include FPGA and ASIC. The controller <NUM> executes information processing relating to the operation of the analysis device <NUM> while controlling each component in the analysis device <NUM>.

The memory <NUM> is one or more memories. Examples of memories that can be used include semiconductor memory, magnetic memory, and optical memory. The memory may function as a main storage device, an auxiliary storage device, or cache memory. The memory <NUM> stores information used for the operation of the analysis device <NUM> and information obtained as a result of the operation of the analysis device <NUM>.

The communication interface <NUM> is one or more communication modules. Examples of communication modules that can be used include communication modules conforming to LAN standards. The communication interface <NUM> receives information used for the operation of the analysis device <NUM>, and transmits information obtained as a result of the operation of the analysis device <NUM>.

The input interface <NUM> is one or more input interfaces. Examples of input interfaces that can be used include physical keys, capacitive keys, pointing devices, and touch screens provided integrally with displays. The input interface <NUM> receives input of information used for the operation of the analysis device <NUM>, from a user.

The output interface <NUM> is one or more output interfaces. Examples of output interfaces that can be used include displays. Examples of displays that can be used include LCDs and organic EL displays. The output interface <NUM> outputs information obtained as a result of the operation of the analysis device <NUM>, to the user.

The meter <NUM> is a near-infrared (NIR) measuring instrument. The meter <NUM> measures the absorbance spectrum of the liquefied gas using near-infrared spectroscopy.

The functions of the analysis device <NUM> are implemented by the processor included in the controller <NUM> executing a property analysis program according to this embodiment. That is, the functions of the analysis device <NUM> are implemented by software. The property analysis program is a program for causing a computer to execute the processes of the steps included in the operation of the analysis device <NUM> to achieve the functions corresponding to the processes of the steps. In other words, the property analysis program is a program for causing the computer to function as the analysis device <NUM>.

All or part of the functions of the analysis device <NUM> may be implemented by the dedicated circuit included in the controller <NUM>. That is, all or part of the functions of the analysis device <NUM> may be implemented by hardware.

The detailed operation of the analysis device <NUM> according to this embodiment will be described below, with reference to <FIG>. The flowchart in <FIG> illustrates the procedure of the property analysis program according to this embodiment.

In step S21, the meter <NUM> measures the absorbance spectrum of the LNG using near-infrared spectroscopy. The meter <NUM> stores the measurement result of the absorbance spectrum of the LNG in the memory <NUM> as the spectrum data <NUM>. The calibration curve <NUM> representing the relationship between the property value and the absorbance spectrum of the sample gas resembling LNG and output from the calibration curve generation system <NUM> is stored in the memory <NUM> beforehand.

In this embodiment, the calibration curve <NUM> representing the relationship among the property value, the temperature, and the absorbance spectrum of the sample gas resembling LNG and output from the calibration curve generation system <NUM> is stored in the memory <NUM> beforehand.

In step S22, the controller <NUM> calculates the property value <NUM> of the LNG, from the calibration curve <NUM> stored in the memory <NUM> and the measurement result of the absorbance spectrum of the LNG obtained by the meter <NUM> in step S21.

Specifically, the controller <NUM> reads the spectrum data <NUM> and calibration curve <NUM> from the memory <NUM>. The controller <NUM> inputs the measurement value of the absorbance spectrum of the LNG flowing in the process line <NUM>, which is indicated by the spectrum data <NUM>, to the calibration curve <NUM>, and acquires the property value <NUM>, such as the concentration of each component of the LNG or the calorific value or density of the LNG, output from the calibration curve <NUM>.

In this embodiment, the measurement result of the temperature of the LNG obtained by the temperature sensor <NUM> is input to the input interface <NUM>. The controller <NUM> calculates the property value <NUM> of the LNG from the calibration curve <NUM> stored in the memory <NUM>, the measurement result of the temperature of the LNG input to the input interface <NUM>, and the measurement result of the absorbance spectrum of the LNG obtained by the meter <NUM>.

In step S23, the controller <NUM> outputs the property value <NUM> of the LNG calculated in step S22, via the communication interface <NUM> or the output interface <NUM>.

As described above, in this embodiment, the measurement device <NUM> including the near-infrared measuring instrument <NUM> and the generation device <NUM> are used to generate the calibration curve <NUM> for converting the absorbance spectrum of the measurement object into the property value such as the concentration of each component contained in the measurement object or the calorific value or density of the measurement object. To generate the calibration curve <NUM>, the gas is cooled to form a liquid. After the generation of the calibration curve <NUM>, the analysis device <NUM> including the near-infrared measuring instrument is used to measure the absorbance spectrum of the LNG, and calculate the property value <NUM> such as the concentration of each component of the LNG or the calorific value or density of the LNG.

Although LNG is subjected to calibration curve generation and property analysis in this embodiment, any sample that can be cooled in the liquefaction chamber <NUM> may be subjected to calibration curve generation and property analysis. For example, a calibration curve covering the composition of LPG whose boiling point at atmospheric pressure is about -<NUM> may be generated. A calibration curve covering the composition of vinyl chloride whose boiling point at atmospheric pressure is about -<NUM> and that is known as a raw material of Saran Wrap® (Saran Wrap is a registered trademark in Japan, other countries, or both) may be generated. The analysis device <NUM> is usable for property analysis not only in an LNG production plant but also in any liquefied gas production plant such as an LPG production plant or a vinyl chloride production plant.

The analysis device <NUM> may be installed and used not only in a liquefied gas production plant but also in any location in which liquefied gas such as LNG is produced, transported, stored, or used.

Advantageous effects according to this embodiment will be described below.

With the measurement device <NUM> according to this embodiment, the spectrum data <NUM> for generating the calibration curve <NUM> can be collected without installing the near-infrared measuring instrument <NUM> in an actual process. By using, as the sample gas, a plurality of samples each adjusted so that the property value covers a desired range, a sufficient amount of spectrum data <NUM> can be collected in a short time. Moreover, the range of the property value can be freely widened. From the collected spectrum data <NUM>, the calibration curve <NUM> representing the relationship between the property value and the absorbance spectrum of liquefied gas can be generated. Thus, by use of the analysis device <NUM> including the near-infrared measuring instrument, the property of the liquefied gas can be analyzed without vaporizing the liquefied gas. This improves the efficiency of liquefied gas property analysis.

According to this embodiment, the sample gas is liquefied in the liquefaction chamber <NUM>, and the sample gas in a liquefied state is irradiated with near-infrared light for measurement in the same liquefaction chamber <NUM>. In this way, the absorbance spectrum of the sample gas in a liquefied state can be measured with high accuracy.

According to this embodiment, both cooling and heating are possible because a coolant and a heater are used in the liquefaction mechanism <NUM>, so that the temperature in the liquefaction chamber <NUM> can be freely regulated.

According to this embodiment, the temperature in the liquefaction chamber <NUM> can be decreased with a simple structure.

According to this embodiment, the introduction tube <NUM> is narrow, which prevents backflow of the sample gas.

According to this embodiment, the temperature sensor <NUM> is installed in the liquefaction chamber <NUM>, so that the temperature of the sample gas in a liquefied state can be measured with high accuracy.

According to this embodiment, the sample gas is injected into the container <NUM> from the buffer tank <NUM> that is filled with the sample gas after vacuuming, so that the purity of the sample gas can be maintained.

With the calibration curve generation system <NUM> according to this embodiment, by using, as the sample gas, a plurality of samples each adjusted so that the property value covers a desired range, a highly versatile calibration curve <NUM>, namely, a universal calibration curve, can be generated in a short time. Moreover, the range of the property value can be freely widened. When analyzing the property of liquefied gas using the analysis device <NUM> including the near-infrared measuring instrument, the property value <NUM> of the liquefied gas can be obtained by applying the measurement result of the absorbance spectrum of the liquefied gas obtained by the near-infrared measuring instrument to the generated calibration curve <NUM>. This improves the efficiency of liquefied gas property analysis.

<FIG> illustrates an example of the range of the property value covered by the calibration curve <NUM> generated in the calibration curve generation system <NUM> and the range of the property value covered by the calibration curve <NUM> generated in the comparative example. C1 in the horizontal axis represents the concentration of methane in LNG, and C2 in the vertical axis represents the concentration of ethane in LNG. As is clear from the example in <FIG>, the concentration range of each component of LNG that can be covered by the calibration curve <NUM> generated in the comparative example is only a small part of the concentration range that can be taken on by the components of LNG. Meanwhile, the calibration curve <NUM> generated in the calibration curve generation system <NUM> can cover nearly the whole concentration range that can be taken on by the components of LNG. Thus, the calibration curve <NUM> generated in the calibration curve generation system <NUM> can cover compositions of LNG produced around the world.

According to this embodiment, the calibration curve <NUM> that also takes the temperature into account is generated, so that an offset in the spectrum measurement result caused by a temperature difference can be corrected.

With the analysis device <NUM> according to this embodiment, the property of the liquefied gas can be analyzed without vaporizing the liquefied gas. This improves the efficiency of liquefied gas property analysis.

Claim 1:
A calibration curve generation method comprising:
liquefying sample gas injected in a container (<NUM>) using a coolant;
measuring an absorbance spectrum of the sample gas in a liquefied state by a near-infrared measuring instrument, via a near-infrared probe extending from inside to outside the container
thereby to obtain a measurement result of the absorbance spectrum of the sample gas for each sample of a plurality of samples that are not natural liquefied natural gas "LNG" or natural liquefied petroleum gas "LPG" and are produced to include the same components as LNG or LPG, but differ from each other in concentration of the components so as to cover an assumed concentration range of each component of LNG or LPG, each sample being injected as the sample gas into the container and liquified; and
executing a chemometrics program (<NUM>) to analyze correlations between the measurement results of the absorbance spectrum of each sample of the plurality of samples, being injected as the sample gas, and the concentration of the components included in each sample
thereby to generate a calibration curve relating an absorbance spectrum of a liquified sample gas and the concentration of each of the components in the sample gas.