JPH07248321A - Gas chromatograph - Google Patents

Abstract

PURPOSE:To prevent any temperature change in a selector valve from occurring as well as to stabilize a base line by conducting a valve driving gas to the selector valve after heating it in use of an analyzing column in a constant temperature oven. CONSTITUTION:A sample conditioner unit 2 is provided with a housing 7 connected to a process-carrier gas supply source 6 through two pipelines 5a and 5b. This housing 7 stores a vaporizer vaporizing sample gas SG parted out of a process, a flow meter, a filter, a selector switch selecting two passages for calibrating standard gas and carrier gas SG, a needle valve or the like inside. A pipeline connecting a pressure reducing valve 21 and a selector valve 15 and conducting a valve driving gas PG to this selector valve 15 is wound on the circumference of an analyzing column 17 in a constant temperature oven 16, so that it is heated by this column 17. Since the valve driving gas PG is heated at the time of passing through the pipeline and fed to the selector valve 15, any temperature drop in the valve 15 is prevented from occurring. The sample gas SG parted out of the process is separated at each gas composition by the column 17, and thus it is detected by a detector 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas chromatograph for performing gas analysis by utilizing a difference in adsorptivity between a packing material packed as a stationary phase in a column and a sample gas, and more particularly to a switching valve using a valve driving gas. The present invention relates to a gas chromatograph capable of stabilizing the baseline by preventing the temperature fluctuation of the.

[0002]

2. Description of the Related Art In a petrochemical process or a steel process, a gas chromatograph has been used as a device for analyzing a component of a process gas and monitoring each process step based on the analysis result and performing various controls. Commonly used by This type of industrial gas chromatograph collects a sample gas from a process line to be measured and sends it to a column by a carrier gas, and in the column, each gas component is adsorbed (affinity) of each component to a stationary phase and After separating by using the difference in moving speed based on the difference in distribution coefficient, it is detected by the detector, the electric signal is processed by the controller, the process is controlled based on this, and the chromatogram waveform is printed out. It is configured to do. For this reason, the gas chromatograph includes a sample conditioner device that separates the sample gas, an analyzer device that separates the sample gas into each gas component and detects the gas component, and an electric device section that drives and controls the gas chromatograph itself. The sample conditioner is a vaporizer that completely vaporizes the sample gas (heavy components) collected from the process line and prevents its condensation, a filter that removes dust in the sample gas,
It is composed of a rotor meter for measuring the flow rates of the sample gas and the standard gas, a needle valve for adjusting the flow rates of the standard gas and the sample gas, and a changeover switch for switching the flow paths. The analyzer device includes first and second columns connected in series, a switching valve, a detector, a heater, a thermostatic chamber, a pressure reducing valve for reducing the gas pressure of carrier gas, and the like. The constant temperature bath
The first and second columns, the switching valve, the detector, etc. are stored,
The inside is kept at the optimum temperature for separation and analysis of sample gas.

[0003]

In such an industrial gas chromatograph, if the temperature of the sample gas or the detector fluctuates, the component concentrations do not match the original sample concentrations, making accurate measurement difficult. Further, in the case where the column is a capillary column, if the temperature fluctuates, the separation performance deteriorates. Therefore, the detector, the switching valve and the column are housed and arranged in the constant temperature tank, and the switching valve is heated by the heater to set and maintain the inside of the constant temperature tank under the optimum temperature condition. However, in practice, the temperature of the drive gas (carrier gas) that drives and controls the switching valve is different from the temperature of the switching valve (usually low), so
Each time the switching valve is switched, the temperature of the switching valve (90 ° -100
There was a problem that the temperature fluctuated. Therefore, the temperature of the detector arranged in the switching valve (about 80 ° C.) also changes, and as shown in FIG. 9, the baseline BL fluctuates before and after the operation of the switching valve, and accurate measurement cannot be performed. The switching valve makes one reciprocating motion every one analysis cycle.

Therefore, in order to solve such a problem,
The temperature of the switching valve is measured by the temperature sensor, and the set point value of the thermistor is corrected by this to automatically control the amount of heat generated by the heater.However, if the temperature of the switching valve changes due to the flow of valve driving gas, The amount of temperature correction also changes each time. In particular, even if the temperature of the switching valve is detected by the temperature sensor, it is only a temperature change near the sensor, and if the heater and the detector are arranged apart from each other, the temperature gradient between them is large and the set point Even if the electric power of the heater is controlled by the value, the temperature around the detector cannot be corrected correctly, and there is a problem that the temperature stability is poor.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to heat a valve driving gas by using an analytical column in a thermostatic chamber. The purpose of the present invention is to provide a gas chromatograph in which the temperature of the switching valve is prevented from fluctuating and the baseline is not disturbed by introducing the gas to the switching valve. Another object of the present invention is to provide a gas chromatograph capable of instantly heating the valve driving gas.

[0006]

In order to achieve the above object, the present invention provides a switching valve for switching between a carrier gas and a sample gas fluid passage in a thermostatic chamber, and a heater and a detector are respectively provided in the switching valve. In the gas chromatograph in which the column for analysis is wound around the switching valve and the valve driving gas is guided from the outside of the constant temperature bath to the switching valve through the pressure reducing valve unit, the pressure reducing valve and the switching valve are arranged. It is characterized in that a pipe for connecting the above and for guiding the valve driving gas to the switching valve is wound around the outer circumference of the analytical column.

[0007]

In the present invention, the pipe connecting the pressure reducing valve and the switching valve and guiding the valve driving gas to the switching valve is heated by the column by being wound around the outer circumference of the analytical column in the constant temperature bath. The valve driving gas is heated as it passes through the piping,
By being supplied to the switching valve, the temperature drop of the switching valve is prevented.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. 1 is a front view showing an embodiment of a gas chromatograph according to the present invention, FIG. 2 is a partially cutaway side view of the gas chromatograph, FIG. 3 is a sectional view of a switching valve and a column structure, and FIG. 4 is a switching valve. FIG. 5 is a view showing a state of the fluid passage during non-measurement, FIG. 5 is a front view of the column unit, and FIG. 6 is a plan view of the bobbin. In FIG. 1, a gas chromatograph for a small process, which is generally denoted by reference numeral 1, includes a sample conditioner device 2, an analyzer device 3 installed and fixed on the sample conditioner device 2, and an analyzer device 3.
And an electric device section 4 provided on the front surface of the.

In FIG. 2, the sample conditioner device 2 includes a housing 7 connected to a process and carrier gas supply source 6 via pipes 5a and 5b. The housing 7 is formed in a box shape with an open upper center, and a vaporizer, a flow meter, a filter for evaporating the sample gas SG separated from the process, a flow path for a standard gas for calibration and a carrier gas CG are provided inside the housing 7. Changeover switch, needle valve (neither shown)
Etc. are stored. Carrier gas CG supplied from the carrier gas supply source 6 to the sample conditioner device 2
As the gas, an inert gas such as nitrogen (N ₂ ) or helium (He) is used. The standard gas for calibration is also the sample gas SG
The same gas as each component gas of is used. The sample gas SG separated from the process is vaporized by the vaporizer, then sent to the analyzer device 3 by the carrier gas CG, separated into each gas component by the column described later, and detected by the detector. Since the vaporizer, the flow meter, the filter, the changeover switch, and the needle valve are not directly related to the present invention, further detailed description will be omitted.

2 and 3, the analyzer device 3 is equipped with an aluminum die-cast analyzer case 10 which is installed and fixed in the upper opening of the sample conditioner device 2. The analyzer case 10 is
The case body 11 is made of an elliptic spherical body whose upper and lower surfaces are open, and is fixed on the sample conditioner device 2 with its major axis oriented in the front-rear direction, and the lid body 12 that closes the upper opening of the case body 11. It forms an explosion-proof case. The case main body 11 has a cylindrical case 13 integrally provided on the front surface, and has a manifold 14, a switching valve 15,
Constant temperature chamber 16 surrounding the switching valve 15, analytical column 17,
Detector 18, heater 19 for heating switching valve 15, analyzer board 20 equipped with electric parts, carrier gas CG
A pressure reducing valve unit 21, a transformer 22 and the like for reducing the pressure (about 5 ± 0.5 Kg / cm ² ) to a predetermined pressure are provided. The manifold 14 is fitted and fixed in the opening on the lower surface of the case body 11, and fixed to the upper surface of a block (not shown) arranged in the housing 7 by bolts 23. Further, the manifold 14 has a plurality of channels 24 for guiding the carrier gas CG and the sample gas SG from the sample conditioner device 2 to the switching valve 15.
Are formed through.

The electric device section 4 includes a printed circuit board 30 and a printed circuit board 30 on which a control circuit for controlling the switching valve 15, the heater 19, the pressure reducing valve unit 21 and the like is formed.
The case main body 1 includes a board fixing bracket 31, a decorative plate 32, a grounding metal 33, a connector 34, etc.
It is housed and arranged in one cylindrical case 13. The front opening of the cylindrical case 13 has a lid 36 having a transparent glass 35.
It is hermetically closed by.

The switching valve 15 will be described in detail with reference to FIGS. 3 and 4. The switching valve 15 includes a plurality of fluid passages (passages a to f shown by solid lines and dotted lines in FIG. 4) formed therein. 40 is switched to guide the sample gas SG to the column 17 and the detector 18 at the time of measurement (indicated by the broken line in FIG. 4), and the passage is switched at the time of non-measurement and backflush to change the carrier gas CG to the column 17 and the detector 18. A conventionally known pneumatically driven diaphragm valve is used. The switching valve 15 includes a center plate 42, a plurality of plungers 45A, 45B ... Which are arranged on the front and back surfaces of the center plate 42 via diaphragms 43, 44, respectively.
45B, which slidably guides and holds, lower plunger plates 46 and 47, and plungers 45A and 45B.
..Alternatively operating the upper and lower pistons 48 and 49,
The return spring 50 for the pistons 48 and 49 is arranged opposite to the center plate 42 with the center plate 42 interposed therebetween.
5A, 45B ..., Plunger plates 46, 47,
The pistons 48 and 49, the return spring 50 and the like are housed, and the main body 51 and the like that form the piston chamber 52 together with the upper lid 53 are provided. The fluid passages 40 are formed so as to penetrate the front and back surfaces of the center plate 42.
Corresponding to each opening of the plunger 45A, 45B ·
.. are arranged facing each other. Pistons 48,4
When the upper and lower plungers 45A, 45B, ... Are alternately operated by 9 to release the pressing state of the diaphragms 43, 44 alternately, the upper and lower plungers 45A, 45B are changed by the gas pressures of the sample gas SG and the carrier gas CG supplied to the switching valve 15. The diaphragms 43 and 44 are elastically deformed alternately to cause the fluid passage 4
The upper route and the lower route of 0 are switched alternately.
In other words, the switching valve 15 is configured such that the diaphragm on the plunger OFF side is elastically deformed by the gas pressure to cause the fluid passage 40.
This is a system in which the lower and upper routes are switched to allow the fluid to flow.

The switching operation of the switching valve 15 will be described in more detail with reference to FIG. 4. By keeping the fluid passages a to f of the switching valve 15 in the solid line state during non-measurement, the first carrier gas introduction port g is used. The supplied carrier gas CG is passed through the column 17 (17A, 17B) to the column 17 and the detector 18, while the sample gas SG introduced from the sample gas introduction port h is discarded from the vent port i via the measuring pipe 56. ing. When the passage of the switching valve 15 is switched from the state of the solid line to the state of the broken line in the measurement, the sample gas SG collected by the measuring pipe 56 is supplied to the column 1 by the carrier gas CG introduced from the second carrier gas introduction port j.
Sent to 7. Although different depending on the sample gas SG, the column 17 is packed with powder having a uniform particle size such as activated carbon, activated alumina, and molecular sieve as a stationary phase, and the stationary phase and each gas component in the sample gas SG The gas components are separated from each other by utilizing the difference in the moving speed based on the difference in the adsorptivity or the distribution coefficient, and the gas components are detected by the detector 18 including a thermal conductivity detector, a flame ionization detector, etc. Convert to signal. This electric signal is proportional to the gas component concentration, and is waveform-processed by a controller (not shown) to monitor or record the process steps. The measuring pipe 56 is formed on the main body 51.

Such a switching valve 15 (pistons 48, 4
As the driving gas of 9), the carrier gas supply source 6 is used.
The carrier gas CG supplied from (FIG. 2) is used. The valve driving gas PG passes through the sample conditioner device 2 and the pressure reducing valve unit 21 and is driven by the driving gas pipe 60 (60a, 60b) into the upper and lower piston side chambers 61a, 61b of the switching valve 15 and the driving gas passage 57a. , 5
Alternately supplied via 7b. Upper piston chamber 61a
Is formed between the inner bottom surface of the upper lid 53 and the upper surface of the piston 48, and the lower piston chamber 61b is formed between the inner bottom surface 51a of the main body 51 and the piston 49.
A heater accommodating hole 63 made of a non-through hole is formed in the outer peripheral surface of the lower end portion of the main body 51 in the radial direction, and the heater 19 is inserted and arranged in the accommodating hole 63. Heater 1
9 has a thermistor, and switches the switching valve 15 to a predetermined temperature (90 °
It is heated and kept at about 100 ° C). Further, a temperature sensor 58 is arranged on the outer peripheral surface of the lower end portion of the main body 51 in the vicinity of the heater 19. The detector 18 is arranged on the upper surface of the upper lid 53. The column structure 6 including the column 17 is provided on the outer peripheral surface on the upper end side of the switching valve 15.
1 is fitted.

The column structure 61 is, as shown in FIG. 3, a cylindrical body 66 commonly fitted to the outer peripheral surfaces of the main body 51 and the upper lid 53, and coaxially fitted to the outer circumference of the cylindrical body 66. It is composed of two column units 67 and 68, a cover 69 that surrounds the outer column unit 68, and an upper lid 71 that covers the upper opening of the tubular body 66. The tubular body 66 is a tubular body with both ends open, has a flange 66A integrally at the lower end of the outer peripheral surface, and is fitted on the outer peripheral surfaces of the main body 51 and the upper lid 53. The flange 66A is in close contact with the upper surface of the lower end portion of the main body 51 and is fixed by a set screw or the like. As shown in FIGS. 5 and 6, the column unit 67 includes a bobbin 74 formed of a cylindrical body with both ends open, and a first column 17A wound around the outer circumference of the bobbin 74.
The bobbin 74 has an inner diameter that is substantially equal to or slightly larger than the outer diameter of the cylindrical body 66, and two column storage grooves 75a and 75b that extend over the entire length in the height direction are formed on the outer peripheral surface at appropriate intervals in the circumferential direction. Has been done. The respective end portions 17a, 17b of the first column 17A wound around the outer peripheral surface of the bobbin 74 are guided upward through the column storage grooves 75a, 75b and are connected to the switching valve 15 at a predetermined connection. Each of them is connected to the mouth via a nipple 77. When the column 17A is wound, the one end 17a thereof is connected to one of the column storage grooves 75a.
Is inserted from above into the outside of the lower end of the column housing groove 75a, and is tightly wound from the bottom to the top on the outer peripheral surface of the bobbin 74. When the column 17A is long, the column 17A is wound in double or triple, and the other end. It suffices to insert the portion 17b into the upper end portion of the other column storage groove 75b and guide it upward. When such column storage grooves 75a and 75b are provided, the column 17A is attached to the bobbin 74.
When wound around, the column portion that intersects the end portion 17a has an advantage that it does not float from the outer peripheral surface of the bobbin and can be prevented from being bent or dented. Then, the column unit 67 thus configured is fitted on the outer periphery of the tubular body 66 and placed on the flange 66A. Although the cylindrical body 66 and the bobbin 74 are shown separated in FIG. 3, it is desirable that they are in close contact with each other in order to improve heat conduction. The other column units 68 are configured in exactly the same manner except that the bobbin 78 around which the second column 17B is wound and the bobbin 74 of the column unit 67 are different in inner and outer diameters. Is omitted. Further, the cover 69 is fitted on the outer circumference of the outer column unit 68 after fitting the column units 67 and 68 onto the outer circumference of the cylindrical body 66 in the ascending order.
Covered by.

By the way, the driving gas pipe 60 (60
a, 60b) is simply penetrated into the constant temperature bath 16, one end of which is connected to the drive passages 57a and 57b of the switching valve 15 and the other end of which is connected to the pressure reducing valve unit 21, respectively, and the upper and lower piston chambers 61a. , 61b is supplied with the valve driving gas PG, the valve driving gas PG is supplied through the pipe 60.
Is usually lower than the temperature of the switching valve 15, so that the temperatures of the switching valve 15, the column 17, and the detector 18 may be lowered to below the optimum temperature condition. Therefore,
In the present invention, the portion of the driving gas pipes 60a, 60b inserted into the constant temperature chamber 16 is lengthened and wound around the outer peripheral surface of the bobbin 80 made of a material having a large thermal conductivity, and the bobbin 80 is It is fitted around the outer circumference of the second column 17B. When the driving gas pipes 60a and 60b are thus wound around the outer periphery of the second column 17B via the bobbin 80, the internal valve driving gas PG is generated by the heat of the column 17B while being supplied to the switching valve 15. Since it is heated, the temperature drop of the switching valve 15 can be prevented. The bobbin 80 is not always necessary and may be directly wound around the outer circumference of the second column 17B.

In this case, when the driving gas pipe 60 is filled with carrier gas heating particles 81 such as glass beads and metal particles of an appropriate size as shown in FIG. 7, the heat capacity of the pipe 60 itself. And the contact area between the valve driving gas PG and the particles 81 increases, so that the valve driving gas P
G can be heated and heated in an instant. The length of the driving gas pipe 60 is determined from the amount required to drive the switching valve 15 once, in consideration of the filling rate of the carrier gas heating particles 81.

The pressure reducing valve unit 21 is composed of, for example, two 3-port solenoid valves and one 5-port solenoid valve, and the carrier gas CG supplied to the analytical column 17 by the two 3-port solenoid valves. The gas pressure is regulated, and the valve driving gas PG is guided to the switching valve 15 without being regulated by one 5-port solenoid valve. Such a pressure reducing valve unit 21 itself is well known in the art.

Thus, in the gas chromatograph having such a structure, the driving gas pipe 60 is installed in the column 1.
Since the valve driving gas PG in the pipe 60 is heated by 7 and supplied to the switching valve 15, the temperature change of the switching valve 15 is small, and therefore the temperature correction by the set point value of the thermistor is performed. The amount can be reduced and the temperature stability can be improved. As a result, as shown in FIG. 8, the change in the baseline BL of the chromatogram can be significantly reduced and prevented as compared with the conventional apparatus. Further, if the fluctuation of the baseline BL is small, it is possible to analyze a low concentration gas component.

[0020]

As described above, according to the gas chromatograph of the present invention, since the pipe for supplying the valve driving gas to the pressure reducing valve unit and the switching valve is wound around the column, the pipe The valve driving gas therein can be heated and heated by the column. Therefore, the temperature of the valve driving gas in the pipe can be made substantially equal to the temperature of the switching valve, and the temperature of the switching valve and the detector can be prevented from lowering. As a result, there is less disturbance in the baseline,
The temperature stability is improved and low concentration components can be analyzed.
In addition, the structure is simple because it is sufficient to lengthen the pipe and wind it around the column.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of a gas chromatograph according to the present invention.

FIG. 2 is a partially cutaway side view of the gas chromatograph.

FIG. 3 is a cross-sectional view of a switching valve and a column structure.

FIG. 4 is a diagram showing a state of the fluid passage when the switching valve is not measured.

FIG. 5 is a front view of a column unit.

FIG. 6 is a plan view of the bobbin.

FIG. 7 is a cross-sectional view of piping.

FIG. 8 is a chromatogram obtained according to the present invention.

FIG. 9 is a chromatogram for explaining the defects of the conventional device.

[Explanation of symbols]

2 ... Sample conditioner device, 3 ... Analyzer device, 15 ... Switching valve, 16 ... Constant temperature chamber, 17 ... Analytical column, 18 ... Detector, 19 ... Heater, 21 ... Pressure reducing valve unit, 60 ... Driving gas pipe, 81 ... Particles for heating carrier gas, PG ... Gas for driving valve.

Claims (1)

[Claims] 1. A switching valve for switching a fluid passage between a carrier gas and a sample gas is provided in a thermostatic chamber, a heater and a detector are respectively provided in the switching valve, and an analytical column is provided on the outer periphery of the switching valve. In a gas chromatograph in which a valve driving gas is guided from the outside of the constant temperature bath to the switching valve through a pressure reducing valve unit in a wound arrangement, the pressure reducing valve and the switching valve are connected and the valve driving gas is guided to the switching valve. A gas chromatograph in which a pipe is wound around the outer circumference of the analytical column.