JP2890238B2 - Gas chromatograph - Google Patents

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 utilizing a difference in adsorbability 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 that prevents a temperature fluctuation of the gas chromatograph and stabilizes a baseline.

[0002]

2. Description of the Related Art In a petrochemical process or a steel process, a gas chromatograph is conventionally used as a device for analyzing the components of a process gas, monitoring each process step based on the analysis result, and performing various controls. Is commonly used. In this type of industrial gas chromatograph, a sample gas is sampled from a process line to be measured, sent to a column by a carrier gas, and each gas component is adsorbed (affinity) on the stationary phase in the column. After separating using the difference in moving speed based on the difference in distribution coefficient, it is detected by the detector, the electrical signal is processed by the controller for waveform processing, and 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 is provided with a sample conditioner device for separating a sample gas, an analyzer device for separating and detecting the sample gas into respective gas components, an electric device for driving and controlling the gas chromatograph itself, and the like. The sample conditioner device completely vaporizes the sample gas collected from the process line and prevents its condensation, a vaporizer that removes dust in the sample gas, a rotameter that measures the flow rates of the sample gas and the standard gas, and a standard gas. And a needle valve for adjusting the flow rate of the sample gas, a changeover switch for switching the flow path, and the like. The analyzer device includes first and second columns, a switching valve, a detector, a heater, a thermostat, a pressure reducing valve for reducing the gas pressure of the carrier gas, and the like, which are connected in series. The constant temperature bath is the first,
A second column, a switching valve, a detector and the like are housed therein, and the inside thereof is maintained at a temperature optimum for separation and analysis of a sample gas.

[0003]

In such an industrial gas chromatograph, when the temperature of the sample gas or the detector fluctuates, the gas components (heavy components) condense, so that the component concentration matches the original sample concentration. And accurate measurement becomes difficult. When the column is a capillary column,
When the temperature fluctuates, the separation performance deteriorates. for that reason,
Detector, switching valve and column are housed and arranged in a thermostat,
The switching valve is heated by the heater, and the inside of the thermostat is set and maintained under the optimum temperature condition. However, in practice, the temperature of the driving gas (carrier gas) for driving and controlling the switching valve is different from the temperature of the switching valve (usually low). ° to 100 °
C) fluctuates greatly. For this reason,
The temperature (about 80 ° C.) of the detector provided in the switching valve also changes. As a result, 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 operates one reciprocation.

Therefore, in order to solve such a problem,
The temperature of the switching valve is measured by the temperature sensor, the set point value of the thermistor is corrected by this, and the heating value of the heater is automatically controlled, but when the temperature of the switching valve changes due to the inflow and outflow of the valve driving gas. The temperature correction amount also changes each time. In particular, even if the temperature of the switching valve is detected by the temperature sensor, it is merely a temperature change in the vicinity of the sensor, and if the heater and the detector are arranged apart from each other, the temperature gradient between the two is large and the set point Even if the power of the heater is controlled by the value, the temperature in the vicinity of the detector cannot be corrected correctly, and there is a problem that the temperature stability is poor.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a heat insulating layer in a piston chamber of a switching valve, and to provide a switching valve,
It is an object of the present invention to provide a gas chromatograph in which the thermal stability is improved by shutting off or reducing the thermal effect of a valve driving gas to and from a temperature sensor, a detector, etc., so that the baseline is not disturbed.

[0006]

In order to achieve the above object, the invention according to the first aspect of the present invention is provided with a center plate sandwiched therebetween and alternately opens fluid passage openings that are opened on both surfaces of the center plate. A switching valve for operating a plunger that opens and closes is operated by a pair of pistons that are also opposed to each other with the center plate interposed therebetween and that is operated by a valve driving gas, and the switching valve is provided with a detector and a heater. In the installed gas chromatograph, a hollow body formed of a heat insulating material is fitted and fixed via a seal member in at least the detector-side piston chamber to which the valve driving gas for driving the piston is supplied. The valve driving gas is guided between the piston and the piston. According to a second aspect of the present invention, there is provided a valve which is opposed to a center plate and alternately opens and closes openings of fluid passages opened on both sides of the center plate. In a gas chromatograph in which a switching valve operated by a pair of pistons operated by a driving gas is provided in a constant temperature chamber, and a detector and a heater are provided in the switching valve, a valve driving gas for driving the piston is provided. At least in the supplied detector-side piston chamber, a telescopic bag formed of heat insulating material is arranged,
The valve driving gas is introduced into the bag, and the piston is operated.

[0007]

According to the first aspect of the present invention, the hollow body forms a heat insulating layer to prevent the temperature of the detector from being lowered by the valve driving gas. According to the second aspect of the present invention, the bag is inflated by the supply of the valve driving gas to drive the piston.
The bag also forms an insulating layer to prevent the temperature of the detector from being lowered by the valve driving gas.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the 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 sectional view of a switching valve and a column structure, and FIG. FIG. 5 is a front view of a column unit, and FIG. 6 is a plan view of a bobbin. In FIG. 1, a small process gas chromatograph generally denoted by reference numeral 1 includes a sample conditioner device 2, an analyzer device 3 fixedly mounted on the sample conditioner device 2, and an analyzer device 3.
And an electric device unit 4 provided on the front surface of the electronic device.

In FIG. 2, the sample conditioner device 2 has a housing 7 connected to a process and a carrier gas supply source 6 via pipes 5a and 5b. The housing 7 is formed in a box shape having an open upper surface center portion. Inside the housing 7, a vaporizer, a flow meter, a filter, and a flow path of a standard gas for calibration and a carrier gas CG for vaporizing the sample gas SG separated from the process are provided. Changeover switch, needle valve (neither is shown)
Etc. are stored. Carrier gas CG supplied to sample conditioner device 2 from carrier gas supply source 6
For example, an inert gas such as nitrogen (N ₂ ) or helium (He) is used. Calibration standard gas is also sample gas SG
The same component gas as described above is used. The sample gas SG fractionated from the process is vaporized by the vaporizer, sent to the analyzer device 3 by the carrier gas CG, separated into each gas component by a column described later, and detected by the detector. In addition, vaporizer,
Since 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 has an analyzer case 10 made of aluminum die-cast and fixed at an opening on the upper surface of the sample conditioner device 2. The analyzer case 10
The case main body 11 is formed of an elliptical sphere having upper and lower surfaces that are open, and is fixed on the sample conditioner device 2 with the long axis directed in the front-rear direction, and a lid 12 that closes an upper opening of the case main body 11. It forms an explosion-proof case. The case main body 11 has a cylindrical case 13 integrally projecting from the front surface, and has a manifold 14, a switching valve 15,
A thermostatic bath 16 surrounding the switching valve 15, an analytical column 17,
A detector 19, a heater 19 for heating the switching valve 15 to maintain the inside of the thermostat 16 at a predetermined temperature, an analyzer board 20 on which electric components are mounted, and a pressure of the carrier gas CG (5 ± 0.5K)
g / cm ² ) to a predetermined pressure.
1, a transformer 22 and the like are provided. The manifold 14 is fitted and fixed to an opening on the lower surface of the case main body 11, and is fixed to an upper surface of a block (not shown) provided in the housing 7 by a bolt 23. The manifold 14 is formed with a plurality of flow paths 24 for guiding the carrier gas CG and the sample gas SG from the sample conditioner device 2 to the switching valve 15.

The electric equipment section 4 includes 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, a board fixing bracket 31 for holding the printed circuit board 30, a decorative board. 32, a grounding bracket 33, a connector 34, and the like.
Is accommodated in the cylindrical case 13. The front opening of the cylindrical case 13 is airtightly closed by a lid 36 provided with a transparent glass 35.

The switching valve 15 will be described in more detail with reference to FIGS. 3 and 4. The switching valve 15 has a plurality of fluid passages formed therein (passage a shown by a solid line and a dotted line in FIG. 4).
To f), the sample gas SG is guided to the column 17 and the detector 18 at the time of measurement (the state shown by the broken line in FIG. 4), and the path is switched to the state shown by the solid line in FIG. Column 1 for gas CG
7 and the detector 18, a conventionally known pneumatically driven diaphragm valve is used. This switching valve 1
5 is a center plate 42 and a center plate 42
A plurality of plungers 45A, 45B,...
, Slidably guide and hold the plungers 45A, 45B,..., And alternately operate the lower plunger plates 46, 47, and the plungers 45A, 45B. , 49, and a main body 51 which is disposed to face the center of the plunger 45A, 45B..., The plunger plates 46, 47, the pistons 48, 49, the return spring 50, and the like. Etc. are provided. The fluid passages 40 are formed so as to penetrate the front and back surfaces of the center plate 42, and the plungers 45A, 45B,... When the upper and lower plungers 45A, 45B,... Are alternately operated by the pistons 48, 49 to release the pressing states of the diaphragms 43, 44 alternately,
The upper and lower diaphragms 43 and 44 are operated by the gas pressure of the sample gas SG and the carrier gas CG supplied to the switching valve 15.
Are alternately elastically deformed, and the upper route and the lower route of the fluid passage 40 are alternately switched. In other words, the switching valve 15 employs a system in which the diaphragm on the plunger OFF side is elastically deformed by the gas pressure of the sample gas SG or the carrier gas CG to switch between the lower route and the upper route of the fluid passage 40 to flow the fluid. It is.

Further, the switching operation of the switching valve 15 will be described in detail with reference to FIG. 4. In the non-measurement time, the fluid passages a to f of the switching valve 15 are maintained in the state of the solid lines, so that the fluid flows from the first carrier gas inlet port g. The supplied carrier gas CG flows to the detector 18 via the column 17 (17A, 17B), while the sample gas SG introduced from the sample gas inlet h is discarded from the vent port i via the measuring pipe 56.
When the passage of the switching valve 15 is switched from the solid line state to the broken line state during measurement, the sample gas SG collected by the measuring pipe 56 is sent to the column 17 by the carrier gas CG introduced from the second carrier gas inlet j. It is. The column 17 is filled with a powder having a uniform particle size, such as activated carbon, activated alumina, or molecular sieve, as a stationary phase, depending on the sample gas SG, and the column 17 is mixed with each gas component in the sample gas SG. Each gas component is separated from each other using the difference in the moving speed based on the difference in the adsorptivity and the distribution coefficient, and this is detected by the detector 18 including a thermal conductivity detector, a flame ionization detector, and the like. Convert to a signal. This electric signal is proportional to the gas component concentration, and is subjected to waveform processing by a controller (not shown) to monitor or record the process steps.
The measuring tube 56 is formed in the main body 51.

The switching valve 15 (pistons 48, 4)
The carrier gas CG supplied from the carrier gas supply source 6 (FIG. 2) is used as the driving gas PG in 9). The valve driving gas PG passes through the sample conditioner device 2 and the pressure reducing valve unit 21 and is supplied to the driving gas passage 5 by the driving gas piping 60 (60a, 60b).
The air is supplied alternately to the upper and lower sides (heater side and detector side) of the switching valve 15 via piston chambers 61a and 61b (FIG. 3) via 7a and 57b. The upper piston chamber 61a is formed between the inner bottom surface of the upper lid 53 and the upper surface of the piston 48,
The lower piston chamber 61b is provided on the inner bottom surface 51a of the main body 51.
And the piston 49. The main body 51
A heater housing hole 62 formed of a non-through hole
Are formed in the radial direction, and the heater 19 is inserted and arranged in the storage hole 62. The heater 19 includes a thermistor, and switches the switching valve 15 to a predetermined temperature (90 ° C to 100 ° C).
Heat). The detector 18 is provided on the upper surface of the upper lid 53. A temperature sensor 58 is provided on the outer peripheral surface of the main body 51 in proximity to the heater 19. A column structure 63 including the column 17 is fitted on the outer peripheral surface on the upper end side of the switching valve 15.

As shown in FIG. 3, the column structure 63 has a cylindrical body 66 commonly fitted on the outer peripheral surfaces of the main body 51 and the upper lid 53, and is coaxially fitted on the outer periphery of the cylindrical body 66. It comprises three column units 67, 68, 69, a cover 70 surrounding the outer column unit 69, an upper lid 71 covering the upper opening of the cylindrical body 66, and the like. Cylinder 66
Is a cylindrical body open at both ends, and a flange 66 is provided at the lower end of the outer peripheral surface.
A is integrally mounted 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 of the main body 51, and is fixed with 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 open at both ends, and a bobbin 7.
4 and a first column 17A wound around the outer periphery of the first column 17A. The bobbin 74 has an inner diameter substantially equal to or slightly larger than the outer diameter of the cylindrical body 66, and two column storage grooves 75a and 75b extending over the entire length in the height direction are formed on the outer peripheral surface at appropriate intervals in the circumferential direction. Have been. Each end 17a, 17b of the first column 17A wound on the outer peripheral surface of the bobbin 74 is
It is guided upward through the column storage grooves 75a and 75b, and is connected to predetermined connection ports opened on the upper surface of the switching valve 15 via nipples 77, respectively. When the column 17A is wound, one end 17a is inserted into the one column storage groove 75a from above, pulled out from the vicinity of the lower end of the column storage groove 75a, and is tightly packed on the outer peripheral surface of the bobbin 74 from bottom to top. When the column 17A is long, the column 17A is wound twice or three times, and the other end 17b is connected to the other column storage groove 75b.
It may be inserted into the upper end portion of the device and guided upward. By providing such column storage grooves 75a and 75b, when the column 17A is wound around the bobbin 74, the column portion intersecting with the end portion 17a is prevented from rising from the outer peripheral surface of the bobbin, and is prevented from being bent or dented. Can have the advantages. Then, the column unit 67 thus configured is fitted on the outer periphery of the cylindrical body 66 and mounted on the flange 66A. Although FIG. 3 shows the cylindrical body 66 and the bobbin 74 separated from each other, it is desirable that the cylindrical body 66 and the bobbin 74 be closely contacted to improve heat conduction. The other column units 68, 69
Is exactly the same except that the inner and outer diameters of the above-mentioned column unit 67 and the bobbin are different, and a description thereof will be omitted. The cover 70 is fitted to the outer periphery of the outermost column unit 69 after fitting the column units 67, 68, 69 in ascending order to the outer periphery of the outermost column unit 69. Will be

By the way, the driving gas piping 60a, 6
0b simply penetrates the thermostat 16 and one end thereof is connected to the switching valve 15
The other end is connected to the drive passages 57a and 57b, and the other end is connected to the pressure reducing valve unit 21, respectively.
When the valve driving gas PG is supplied to 1a and 61b, the piping 6
The temperature of the valve driving gas PG supplied through the inside of 0 is lower than the temperature of the normal switching valve 15, so that the temperatures of the switching valve 15, the column 17, and the detector 18 are lowered below the optimum temperature condition. There is a risk. Therefore, in the present invention, the upper piston chamber 61a on the detector 18 side and the heater 1
A hollow body 80 made of a heat-insulating material is fitted and fixed in the lower piston chamber 61b on the 9 side via an O-ring 81, and the gaps between the hollow body 80 and the pistons 48 and 49 are respectively set in the upper and lower piston chambers. The valve driving gas PG is introduced into the gap to drive the pistons 48 and 49 alternately. The O-ring 81 is fitted in an annular groove formed on the outer peripheral surface of the hollow body 80. The reason for using the O-ring 81 is that the upper and lower piston chambers 61a and 61a
The valve driving gas PG supplied to 1b enters the upper surface and the lower surface side of the hollow body 80 through the gap between the outer peripheral surface of the hollow body 80 and the inner wall surface of the main body 51, respectively.
This is to prevent cooling of the inner bottom surface 1b and the inner bottom surface 51b.

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 analysis column 17 by the two 3-port solenoid valves. And the valve driving gas PG is guided to the switching valve 15 without adjusting the pressure by one 5-port solenoid valve. Such a pressure reducing valve unit 21 itself is conventionally known.

Thus, in such a configuration, the hollow body 80 made of an insulating material and the air layer confined therein insulate the upper and lower piston chambers 61a, 61b and the main body 51 from each other. The main body 51 is not remarkably cooled by the valve driving gas PG every time the valve 15 is driven, so that the temperature change of the switching valve 15 and the detector 18 can be reduced. Therefore, the amount of temperature correction based on the set point value of the thermistor can be reduced, and the temperature stability can be improved. As a result, as shown in FIG.
L fluctuation can be significantly reduced and prevented as compared with the conventional apparatus. In addition, if the fluctuation of the baseline is small, it is possible to analyze a low-concentration gas component.

In this case, a part of the inner wall surface of the main body 51 is cooled by the valve driving gas PG because it is exposed to the upper and lower piston chambers 61a and 61b, but its area is equal to that of the ceiling surface 51a and the inner bottom surface 51b. The body 51 is smaller than the area.
Does not have a significant effect on the temperature drop. In this embodiment, the upper piston chamber 61a on the detector 18 side and the lower piston chamber 61b on the heater 19 and temperature sensor 58 side are used.
And the hollow bodies 80 are arranged respectively,
Upper piston chamber 61 on the side of the detector 18 which is susceptible to fluctuation of L
There is an effect even if it is arranged only in a.

FIG. 8 is a sectional view of a main part showing another embodiment of the present invention. In this embodiment, the hollow body 80 shown in the above embodiment is used.
Instead, a flexible bag 90 made of a heat insulating material such as rubber or vinyl is provided in the lower piston chamber 61b (the same applies to the upper piston chamber), and the bag 90 is inflated by the valve driving gas PG. The structure is such that the piston 49 is driven. The displacement of the piston 49 is 0.3
mm, the extension of the bag 90 may be very slight. Such a configuration has an advantage that the O-ring 81 in the above embodiment is unnecessary because the bag 90 itself also serves as a sealing member.

[0021]

As described above, according to the gas chromatograph of the present invention, at least the detector-side piston chamber and the switching valve are insulated by a hollow body made of a heat insulating material or an elastic bag, so that the valve drive The temperature change of the detector due to the gas can be reduced. As a result, the amount of temperature correction is small, the temperature stability is improved, the disturbance of the baseline is small, and the analysis of low concentration components is possible.
In addition, when the elastic bag is used, no seal member is required, and the structure is simple.

[Brief description of the drawings]

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

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

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

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

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

FIG. 6 is a plan view of a bobbin.

FIG. 7 is a chromatogram obtained by the present invention.

FIG. 8 is a sectional view of a main part showing another embodiment of the present invention.

FIG. 9 is a chromatogram for explaining a disadvantage of the conventional apparatus.

[Explanation of symbols]

2 ... Sample conditioner device, 3 ... Analyzer device, 15 ... Switching valve, 16 ... Constant temperature bath, 17 ... Analysis column, 18 ... Detector, 19 ... Heater, 21 ... Pressure reducing valve unit, 40 ... Fluid passage, 42 ... Center plate, 45
A, 45B: plunger, 48: piston, 49: piston, 60: driving gas pipe, 61a: upper piston chamber, 61b: lower piston chamber, 80: hollow body, 81: O
Ring, 90: bag, PG: valve driving gas.

Claims (2)

(57) [Claims] 1. A plunger which is opposed to a center plate and alternately opens and closes openings of fluid passages opened on both sides of the center plate is provided by a valve driving gas also opposed to the center plate. In a gas chromatograph in which a switching valve operated by a pair of operated pistons is disposed in a constant temperature bath, and a detector and a heater are disposed in the switching valve, at least a valve driving gas for driving the piston is supplied. A gas chromatograph characterized in that a hollow body formed of a heat insulating material is fitted and fixed in a detector-side piston chamber via a sealing member, and the valve driving gas is introduced between the hollow body and the piston. . 2. A plunger which is opposed to the center plate and alternately opens and closes openings of fluid passages opened on both sides of the center plate is provided by a valve driving gas which is also opposed to the center plate. In a gas chromatograph in which a switching valve operated by a pair of operated pistons is disposed in a constant temperature bath, and a detector and a heater are disposed in the switching valve, at least a valve driving gas for driving the piston is supplied. A gas chromatograph characterized in that a telescopic bag formed of a heat insulating material is disposed in a detector-side piston chamber, and the valve driving gas is guided into the bag to operate the piston.