JPH07248320A - Gas chromatograph - Google Patents

Abstract

PURPOSE:To make improvements in temperature stability and a base line so as not to fall into disorder by installing a heat insulating layer in a piston chamber of a selector valve, and interrupting or relieving any thermal effect due to the run of valve driving gas to the selector valve, a temperature sensor, a detector or the like. CONSTITUTION:Each hollow body 80 formed by a heat insulator is inserted tight into both upper and lower piston chambers 61a and 61b of a selector valve 15 via an O-ring 81. With these hollow bodies 80, an interval between these upper and lower piston chambers 61a, 61b and a body 51 is insulated from heat.

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 collected from the process line and prevents its condensation, a filter that removes dust in the sample gas, a rotameter that measures the flow rates of the sample gas and standard gas, and a standard gas. And a needle valve for adjusting the flow rate of the sample gas, a changeover switch for changing over the flow path, and the like. The analyzer device includes first and second columns connected in series, a switching valve, a detector, a heater, a constant temperature bath, a pressure reducing valve for reducing the gas pressure of the carrier gas, and the like. The constant temperature bath is the first,
A second column, a switching valve, a detector, etc. are housed and the inside is kept at an optimum temperature for the sample gas separation and analysis.

[0003]

In such an industrial gas chromatograph, when the temperature of the sample gas or the detector fluctuates, the gas component (heavy component) condenses, so that the component concentration does not match the original sample concentration. Therefore, accurate measurement becomes difficult. If the column is a capillary column,
When the temperature fluctuates, the separation performance deteriorates. for that reason,
Store the detector, switching valve and column in a thermostatic chamber,
The switching valve is heated by the heater, and the inside of the constant temperature bath is set and maintained under optimum temperature conditions. 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 the temperature of the switching valve (90 ° ~ 100 °
There is a problem that C) varies greatly. For this reason,
The temperature (about 80 ° C) of the detector arranged in the switching valve also changes. As a result, the baseline BL fluctuates before and after the operation of the switching valve as shown in FIG. 9, and accurate measurement cannot be performed. The switching valve reciprocates once.

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 provide a heat insulating layer in the piston chamber of the switching valve,
An object of the present invention is to provide a gas chromatograph in which the thermal stability is improved and the baseline is not disturbed by blocking or reducing the thermal influence caused by the inflow and outflow of the valve driving gas with respect to the temperature sensor, the detector and the like.

[0006]

In order to achieve the above-mentioned object, the invention according to claim 1 is arranged opposite to each other with a center plate interposed therebetween, and the opening portions of the fluid passages opened on both sides of the center plate are alternately arranged. A switching valve for operating a plunger that opens and closes is also installed in the thermostatic chamber so as to be operated by a pair of pistons, which are also opposed to each other with the center plate interposed therebetween, and a detector and a heater are arranged in the switching valve. In the gas chromatograph provided, at least the detector-side piston chamber to which the valve driving gas for driving the piston is supplied, a hollow body formed of a heat insulating material is fitted and fixed via a seal member, The valve driving gas is introduced between the piston and the piston. In the invention according to claim 2, the plungers that are opposed to each other with the center plate sandwiched therebetween and that alternately open and close the openings of the fluid passages that open on both sides of the center plate are also installed oppositely with the center plate sandwiched therebetween. In a gas chromatograph in which a switching valve operated by a pair of pistons operated by driving gas is arranged in a constant temperature bath, and a detector and a heater are arranged in the switching valve, the valve driving gas for driving the piston is An expandable bag made of a heat insulating material is provided in at least the detector-side piston chamber that is supplied.
It is characterized in that the valve driving gas is introduced into the bag to operate the piston.

[0007]

In the invention of claim 1, the hollow body forms a heat insulating layer to prevent the temperature of the detector from being lowered by the valve driving gas. In the invention of claim 2, the bag is inflated by the supply of the valve driving gas to drive the piston.
In addition, the bag forms an insulating layer to prevent the temperature of the detector from being lowered by the valve driving gas.

[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 component gas as 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. In addition, the vaporizer,
The flow meter, the filter, the changeover switch, and the needle valve are not directly related to the present invention, and thus detailed description thereof 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,
The detector 18, the heater 19 for heating the switching valve 15 to keep the inside of the constant temperature bath 16 at a predetermined temperature, the analyzer board 20 equipped with electric parts, the pressure of the carrier gas CG (5 ± 0.5K
pressure reducing valve unit 2 for reducing the pressure (about g / cm ² ) to a predetermined pressure
1, a transformer 22 and the like 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, a plurality of flow passages 24 that lead the carrier gas CG and the sample gas SG from the sample conditioner device 2 to the switching valve 15 are formed through the manifold 14.

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, etc. is formed, a board fixing bracket 31 for holding the printed circuit board 30, and a decorative plate. 32, a grounding metal 33, a connector 34, etc.
It is housed and arranged in the cylindrical case 13. The front opening of the cylindrical case 13 is hermetically closed by a lid 36 having 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 (a passage a shown by a solid line and a dotted line in FIG. 4).
~ F) 40 is switched, the sample gas SG is guided to the column 17 and the detector 18 at the time of measurement (state of the broken line in FIG. 4), and the passage is switched to the state of the solid line at FIG. Column 1 for gas CG
A pneumatically driven diaphragm valve, which is well known in the art, is used to guide the detector 7 and the detector 18. This switching valve 1
5 is a center plate 42 and a center plate 42
Plural plungers 45A, 45B, which are arranged opposite to each other on the front and back sides of the diaphragms 43, 44, respectively.
, Slidably guiding and holding the plungers 45A, 45B, ..., Alternately operating the lower plunger plates 46, 47 and the plungers 45A, 45B. , 49 of the return spring 50 and the plungers 45A, 45B, ..., Plunger plates 46, 47, pistons 48, 49, return spring 50, etc., which are arranged to face each other with the center plate 42 interposed therebetween. And so on. The fluid passage 40 is formed so as to penetrate through the front and back surfaces of the center plate 42, and the plungers 45A, 45B ... Are arranged to face each other corresponding to the respective openings of the fluid passage 40. When the upper and lower plungers 45A, 45B ... Are alternately operated by the pistons 48, 49 to release the pressing state of the diaphragms 43, 44 alternately,
The upper and lower diaphragms 43, 44 are controlled by the gas pressures 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. That is, the switching valve 15 adopts 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. Is.

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 detector 18, while the sample gas SG introduced through the sample gas introduction port h is discarded through the measuring pipe 56 and the vent port i.
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 introduction port j. Be done. 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 PG of 9), the carrier gas CG supplied from the carrier gas supply source 6 (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) to form the driving gas passage 5.
It is alternately supplied to the upper and lower (heater side and detector side) piston chambers 61a and 61b (FIG. 3) of the switching valve 15 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 has an inner bottom surface 51a of the main body 51.
And the piston 49. The main body 51
On the outer peripheral surface of the lower end side of the
Are formed in the radial direction, and the heater 19 is inserted and arranged in the housing hole 62. The heater 19 includes a thermistor and keeps the switching valve 15 at a predetermined temperature (90 ° to 100 ° C).
Heat) to keep it warm. The detector 18 is arranged on the upper surface of the upper lid 53. Further, a temperature sensor 58 is arranged on the outer peripheral surface of the main body 51 close 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 that is commonly fitted to the outer peripheral surfaces of the main body 51 and the upper lid 53, and is coaxially fitted to the outer circumference of the cylindrical body 66. It is composed of three column units 67, 68, 69, a cover 70 surrounding the outer column unit 69, an upper lid 71 for covering the upper opening of the cylindrical body 66, and the like. Tube 66
Is a tubular body with both ends open, and a flange 66 is provided on the lower end of the outer peripheral surface.
A is integrally formed and is fitted to 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 whose both ends are open, and a bobbin 7.
4 and a first column 17A wound around the outer circumference of the No. 4 column. 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
It is guided upward through the column storage grooves 75a and 75b, and is connected to a predetermined connection port opened on the upper surface of the switching valve 15 via a nipple 77, respectively. When winding the column 17A, one end 17a of the column 17A is inserted into one of the column storage grooves 75a from above and drawn out from the vicinity of the lower end of the column storage groove 75a to the outside, and the outer peripheral surface of the bobbin 74 is packed from bottom to top. In the case where the column 17A is long, the column 17A is wound in double or triple, and the other end 17b is inserted into the other column storage groove 75b.
Insert it at the upper end of the and guide it upward. By providing such column storage grooves 75a and 75b, when the column 17A is wound around the bobbin 74, the column portion that intersects the end portion 17a is prevented from rising from the outer peripheral surface of the bobbin and is prevented from being bent or dented. It has the advantage that it can. 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. In addition, other column units 68, 69
The column unit 67 and the bobbin have the same configuration except that the inner and outer diameters of the bobbin are different from each other, and the description thereof will be omitted. Further, the cover 70 is fitted on the outer circumference of the outermost column unit 69 after fitting the column units 67, 68, 69 in the ascending order on the outer circumference of the cylindrical body 66, and then the lid 71 covers the upper end opening. Be seen.

By the way, the driving gas pipes 60a, 6
0b is simply penetrated into the constant temperature bath 16 and one end thereof is provided with the switching valve 15
Of the upper and lower piston chambers 6 by connecting the other end to the pressure reducing valve unit 21 to the drive passages 57a and 57b.
When the valve driving gas PG is supplied to 1a and 61b, the pipe 6
The temperature of the valve-driving gas PG supplied through 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 9th side through an O-ring 81, and the clearance between the hollow body 80 and the pistons 48, 49 is set in the upper and lower piston chambers, respectively. 61a and 61b are provided, and the valve driving gas PG is introduced into this gap to alternately drive the pistons 48 and 49. 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, 61a, 6
The valve-driving gas PG supplied to 1b enters the upper surface and the lower surface 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, and the ceiling surface 5 of the main body 51
This is to prevent the 1a and the inner bottom surface 51b from being cooled.

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 such a structure, the hollow body 80 made of an insulating material and the air layers trapped inside the hollow body 80 insulate the upper and lower piston chambers 61a and 61b from the main body 51, respectively. The main body 51 is not significantly cooled by the valve driving gas PG every time the valve 15 is driven, and 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. 7, the baseline B of the chromatogram
It is possible to prevent the L fluctuation from being significantly reduced as compared with the conventional device. If the baseline fluctuation is small, it is possible to analyze low-concentration gas components.

In this case, a part of the inner wall surface of the main body 51 is exposed to the upper and lower piston chambers 61a and 61b and thus is cooled by the valve driving gas PG, but the area thereof is that of the ceiling surface 51a and the inner bottom surface 51b. Smaller than the area, the main body 51
It does not have a large effect on the temperature drop of. Further, 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.
A hollow body 80 is provided in each of the
Upper piston chamber 61 on the detector 18 side that is susceptible to fluctuations in L
Even if it is provided only in a, it is effective.

FIG. 8 is a cross-sectional view of an essential part showing another embodiment of the present invention. In this embodiment, the hollow body 80 shown in the above embodiment is used.
By disposing an expandable bag 90 made of a heat insulating material such as rubber or vinyl in the lower piston chamber 61b (the same applies to the upper piston chamber) and inflating the bag 90 with the valve driving gas PG. It is configured to drive the piston 49. Displacement of piston 49 is 0.3
Since the bag 90 has a size of about mm, the bag 90 need only be slightly stretched. In such a configuration, since the bag 90 itself also serves as a seal member, there is an advantage that the O-ring 81 in the above embodiment is not necessary.

[0021]

As described above, according to the gas chromatograph according to the present invention, at least the detector-side piston chamber and the switching valve are insulated by the hollow body or the expandable bag made of a heat insulating material, so that the valve is driven. The temperature change of the detector due to the gas can be reduced. As a result, the temperature correction amount is small, the temperature stability is improved, the disturbance of the baseline is small, and the low-concentration component can be analyzed.
Further, when the expandable bag is used, the sealing member is not required and the structure is simple.

[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 chromatogram obtained according to the present invention.

FIG. 8 is a cross-sectional view of essential parts showing another embodiment of 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, 40 ... Fluid passage, 42 ... Center plate, 45
A, 45B ... Plunger, 48 ... Piston, 49 ... Piston, 60 ... Driving gas piping, 61a ... Upper piston chamber, 61b ... Lower piston chamber, 80 ... Hollow body, 81 ... O
Ring, 90 ... Bag, PG ... Valve driving gas.

Claims (2)

[Claims] 1. Plungers that are arranged opposite to each other with a center plate sandwiched therebetween and that alternately open and close the openings of fluid passages that open on both sides of the center plate are also paired with the center plate sandwiched by a valve driving gas. In a gas chromatograph in which a switching valve operated by a pair of operated pistons is arranged in a thermostatic chamber, and a detector and a heater are arranged 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 seal member, and the valve driving gas is guided between the hollow body and the piston. . 2. Plungers that are arranged opposite to each other with a center plate sandwiched therebetween and that alternately open and close the openings of fluid passages that open on both sides of the center plate are also paired with the center plate sandwiched by a valve driving gas. In a gas chromatograph in which a switching valve operated by a pair of operated pistons is arranged in a constant temperature bath, and a detector and a heater are arranged in the switching valve, at least a valve driving gas for driving the piston is supplied. A gas chromatograph characterized in that a stretchable bag made of a heat insulating material is arranged in the detector side piston chamber, and the valve driving gas is introduced into this bag to operate the piston.