Flame photometric detector

Abstract

A flame photometric detector for a process gas chromatograph is provided. The flame photometric detector includes a combustion chamber body that defines a combustion chamber within the combustion chamber body. A sample inlet tube is configured to introduce a process gas sample into the combustion chamber. An igniter is configured to initiate combustion within the combustion chamber. A thermocouple assembly is configured to provide an indication of the temperature within the combustion chamber. The sample tube has an end that is adjustable relative to the combustion chamber.

Description

Technical Field

[0001] The invention relates to a flame photometry detector. Background Art

[0002] Gas chromatography is the separation of a mixture of chemical compounds due to their migration rate through a chromatographic column. This separates compounds based on differences in boiling point, polarity, or molecular size. The separated compounds then flow through a suitable detector, such as a flame photometric detector (FPD), which determines the presence and / or concentration of each compound represented in the entire sample. Knowing the concentration or presence of various compounds allows the calculation of certain physical properties, such as BTU or specific gravity, using industry standard equations.

[0003] In operation, a sample is typically injected into a chromatographic column filled with a packing material. Typically, the packing material is referred to as the "stationary phase" because it remains fixed within the chromatographic column. A supply of inert carrier gas is then provided to the chromatographic column to force the injected sample through the stationary phase. The inert gas is referred to as the "mobile phase" because it is transported through the chromatographic column.

[0004] As the mobile phase pushes the sample through the column, various forces cause the components of the sample to separate. For example, heavier components move slower through the column than lighter components. The separated components leave the column in a process called elution. The resulting components are then fed into a detector that responds to certain physical properties of the eluted components.

[0005] One type of detector is called a flame photometer. A flame photometer uses a photomultiplier tube to detect the spectral lines of a compound as it burns in a flame. The compound eluted from the column is brought into a flame, usually fueled by hydrogen, which excites specific elements in the molecule, and the excited elements (P, S, halogens, some metals) emit light with specific characteristic wavelengths. The emitted light is filtered and detected by a photomultiplier tube. In particular, phosphorus emits about 510nm to 536nm, while sulfur emits about 394nm. Summary of the invention

[0006] A flame photometer for a process gas chromatograph is provided. The flame photometer includes a combustion chamber body defining a combustion chamber in the combustion chamber body. A sample inlet tube is configured to introduce a process gas sample into the combustion chamber. An igniter is configured to initiate combustion in the combustion chamber. A thermocouple assembly is configured to provide an indication of a temperature within the combustion chamber. The sample tube has an end that is adjustable relative to the combustion chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1is a schematic diagram of a process gas chromatograph using a known flame photometer cart solution according to the prior art.

[0008] Figure 2 is a schematic diagram of a process gas chromatograph that may be used with embodiments of the present invention.

[0009] Figure 3 is a system schematic diagram of a gas chromatograph according to an embodiment of the present invention.

[0010] Figure 4 is a magnified view of a prior art flame photometer used in a sidecar solution.

[0011] Figure 5 is a schematic perspective view of a gas chromatograph and a flame photometer according to an embodiment of the present invention.

[0012] Fig. 6A and Figure 6B is a cross-sectional view of a flame photometer according to the prior art.

[0013] Fig. 7A and Figure 7B 3 and 4 respectively show a perspective view and a side view of a miniature flame photometer according to an embodiment of the present invention.

[0014] FIG. 7C to FIG. 7F 1 are various schematic sectional views and cross-sectional views of a miniature flame photometer according to an embodiment of the present invention.

[0015] Figure 8 is a perspective view of a combined thermocouple / igniter assembly for a miniature flame photometer according to an embodiment of the present invention.

[0016] Fig. 9 is an exploded view of a combined thermocouple / igniter assembly for a miniature flame photometer according to an embodiment of the present invention.

[0017] Fig.10 is a cross-sectional view of a sample tube assembly of a miniature flame photometer according to an embodiment of the present invention.

[0018] Fig.11 The invention relates to a gas mixer of a miniature flame photometer according to an embodiment of the present invention.

[0019] Fig.12 is a cross-sectional view of a miniature flame photometer according to an embodiment of the present invention. DETAILED DESCRIPTION

[0020] Conventional flame photometer burners typically include: a flame chamber, an external overhead exhaust path, an igniter, a thermocouple, and a gas mixer. In some relatively small footprint applications, such as explosion-proof gas chromatography applications, it may be helpful to minimize the physical size of the flame photometer so that it can fit within a dedicated temperature-controlled furnace. A micro burner for a flame photometer (FPD) can be provided that includes an internal exhaust path and an integrated igniter / thermocouple.

[0021] According to the embodiments described below, the miniature flame photometer can be installed in such a small footprint application. In some examples described below, the miniature flame photometer can include a substantially semicircular flame chamber having a reduced size relative to previous designs. In addition, in some examples, an integrated sample tube is used to position the end of the sample tip at a precise location in the mixed gas flow so as to minimize the workload of the tip adjustment and maximize the response of the miniature flame photometer.

[0022] Figure 1 Schematic diagram of a process gas chromatograph 20 using a known flame photometer side-cart solution according to the prior art. The side-cart 10 is shown close to the process gas chromatograph 20 and is coupled to the process gas chromatograph 20 via a plurality of pipelines. This side-cart solution is typically used because the flame photometer of the side-cart 10 cannot physically fit within the space-limited explosion-proof furnace 22 of the process gas chromatograph 20.

[0023] Before describing the flame photometric detector in detail, it is useful to first generally describe the process gas chromatograph used with the flame photometric detector.

[0024] Figure 2 is a schematic diagram of a process gas chromatograph that may be used with embodiments of the present invention. Figure 1 A 700XA gas chromatograph 100 available from Rosemount Inc. (Emerson Automation Solutions) is shown, and the methods and embodiments provided herein may be used with other exemplary gas analyzers. This may include a 1500XA process gas chromatograph and a 570 gas chromatograph available from Rosemount, as well as various other types and models of gas chromatographs. In addition, it is contemplated that a variety of other devices other than gas chromatographs may be used with embodiments of the present invention. For example, Figure 2As shown, process gas chromatograph 100 includes a user interface 102 having a display and one or more user input mechanisms 104. Additionally, process gas chromatograph 100 includes a temperature controlled oven 106. Components within oven 106 may be maintained at very precisely controlled temperatures to facilitate an analytical process.

[0025] Figure 3 200 is a system schematic diagram of a gas chromatograph according to an embodiment of the present invention. Although an example of a gas chromatograph 200 will now be provided, it should be understood that the gas chromatograph 200 can take a variety of other forms and configurations. For example, it should be understood that the gas chromatograph 200 can have other configurations for columns, valves, detectors, etc. However, in this example, the gas chromatograph 200 illustratively includes a carrier gas inlet 202, a sample inlet 204, a sample outlet 206, and a measurement outlet 208. In operation, a carrier gas is provided to a flow panel 210, which passes through a regulator 212 and a dryer 214 at the flow panel 210 before entering a temperature-controlled analyzer furnace 216 and passing through a carrier gas preheater 218.

[0026] During measurement, sample gas enters the chromatograph 200 via the sample inlet 204 and enters the analyzer oven 216. The sample gas (during measurement) or the calibration gas (during calibration) and the carrier gas ultimately enter a plurality of pneumatically controlled multi-port selector valves 260 to selectively flow various volumes of sample and / or carrier gas through various chromatographic columns 222 in accordance with known gas chromatography techniques. Each of the pneumatically controlled multi-port selector valves 260 is fluidly coupled to a corresponding solenoid 224 that receives a control signal for the solenoid from a controller 226. In addition, the controller 226 may be coupled to one or more temperature sensors within the oven 216 and one or more heaters thermally coupled to the oven 216 to provide temperature control for the oven 216. However, it is also contemplated that a thermal control system separate from the controller 226 may also be used.

[0027] In addition, if Figure 3As shown, each pneumatically controlled multi-port selector valve 260 has a pair of states. In the first state, the fluid connection of each valve 260 is shown in solid lines. In the second state, the fluid connection of each valve 260 is shown in dotted lines. The controller 226 is operably connected to the detector 228, which is a flame photometer, which will be described in more detail below. Therefore, the controller 226 can fully control the flow through the gas chromatograph 200 by means of the control solenoid 224. In addition, the controller 226 can determine the response of the detector 228 in order to detect or otherwise characterize various species in the sample gas. In some embodiments, the controller 226 receives the control signal from the control module 34 ( Figure 4 ) reads the analog signal. In addition, the controller 226 can characterize, calculate and identify the peaks in the chromatogram. In this way, the controller 226 can selectively introduce the sample into the chromatographic column within a selected amount of time, reverse the gas flow through the chromatographic column, and guide the reversed gas flow through the detector to observe and / or record the detector response over time. This provides a chromatographic analysis of the sample.

[0028] Figure 4 2 is an enlarged view of a flame photometer of the prior art used in a side cart solution. As shown, the flame photometer burner 30 is positioned near the photomultiplier tube module 32. The control module 34 is disposed above the photomultiplier tube module 32 and controls the burner 30 and the photomultiplier tube module 32. In the example, the control module 34 processes and amplifies the response signal from the photomultiplier tube module 32 and provides the response signal to a suitable processing device such as the controller 226.

[0029] According to the embodiments described herein, Figure 5 As shown, a miniature flame photometer is provided, which rearranges the three main components of the flame photometer by disassembling the flame photometer burner and the photomultiplier module, and combines the control module and the photomultiplier module. As can be seen, the miniature flame photometer 300 is connected to the photomultiplier tube and the control module 302 via an optical fiber cable 304. According to one embodiment, the miniature flame photometer 300 can be completely assembled in the volume of the temperature-controlled furnace 22 of the process gas chromatograph. Accordingly, the entire side cart in the past can now be roughly assembled in the gas chromatograph housing.

[0030] Relative to Figure 4 Some of the structural changes that facilitate these significant changes are related to Figure 5 is shown and is facilitated by changes in the design of the flame photometer itself.

[0031] Fig. 6Aand Figure 6B is a cross-sectional view of a flame photometer according to the prior art. Figure 6B It is along Fig. 6A The cross-sectional view taken along line BB in FIG. Fig. 6A and Figure 6B As shown, a typical flame photometer burner 400 of a gas chromatograph is arranged as shown. The detector 400 has a mounting portion 421, which is used to connect to optical devices and photomultiplier tubes. During operation, air enters through accessory 417, and hydrogen enters through accessory 415. Column outflow (sample) gas is provided through sample tube 423. Air and hydrogen are mixed at gas mixer 414 and enter combustion chamber 412. Ignitor 419 ignites the flame, and the gas burns in combustion chamber 412. Thermocouple 413 monitors the state of the flame, and the burned gas is discharged through the exhaust path 410 of accessory 411. Light with a specific wavelength is generated from the flame and detected. The response of the flame photometer is very sensitive to the end position 418 of the sample tube 423 relative to the gas mixer 414. With the same gas mixing ratio, the response of the flame photometer can be maximized by moving the sample tube 423 up and down. For most applications (eg, detection of sulfur components in natural gas), it is necessary for safety reasons to properly vent the burned gases from the flame photometer burner.

[0032] Fig. 7A and Figure 7B 500 are perspective and side views of a micro flame photometer according to an embodiment of the present invention. In order to effectively route the exhaust gas from the combustion flame, the internal exhaust path within the micro flame photometer 500 reroutes the exhaust accessories to the exact location required to minimize the physical size of the burner and simplify the piping. These internal flow paths of the embodiments of the present invention are Figure 7C , Fig.7D and Fig. 7E The micro flame photometer 500 includes a combustion chamber body 510 , a connector 512 and a cover 511 .

[0033] For the sake of clarity, Figure 7C It is along Figure 7B A cross-sectional view taken along line AA in FIG. Fig.7D It is along Figure 7B A cross-sectional view taken along line BB in FIG. Fig. 7E It is a partial cross-sectional view of a miniature flame photometer. Figure 7F is from Fig.7D An enlarged cross-sectional view taken at circle “C” in FIG.

[0034] Air typically enters the burner through fitting 516, hydrogen enters the burner through fitting 517, and sample gas from the column enters the burner through fitting 530. Air and hydrogen are mixed at gas mixer 518 and burned in combustion chamber 560. The burned gas then passes through exhaust paths 540A and 540B of the combustion chamber body 510, paths 541A, 541B and 541C of connector 512, and then is discharged through path 542 of fitting 514. The cross-drilled holes for the exhaust paths can be simply plugged by standard steel balls 513A and 513B to simplify and minimize the physical size of the burner. However, the exhaust paths can be plugged in any suitable manner.

[0035] Figure 8 is a perspective view of a combined thermocouple / igniter assembly for a miniature flame photometer according to an embodiment of the present invention. Figure 8 In the structure shown, the igniter and thermocouple required for the flame photometer are integrated. This integrated structure 550 only requires a single entry Fig.7D and Fig. 7E Combustion chamber 560 is shown in FIG.

[0036] Fig. 9 is an exploded view of a combined thermocouple / igniter assembly for a miniature flame photometer according to an embodiment of the present invention. The integrated temperature sensing igniter 550 is typically constructed of a high temperature insulating material, such as a ceramic tube 552 having four holes extending axially therethrough. The igniter 551 and the thermocouple 553 extend through two of the holes, and the leads 551A and 551B of the igniter 551 pass through the holes 552A and 552B of the ceramic tube 552. The leads 553A and 553B pass through the holes 552C and 552D of the ceramic tube 552. The leads 551A, 551B, 553A, and 553B are operably connected to the controller 226 or other suitable circuitry to control ignition and detect the temperature within the combustion chamber 560. The four-hole ceramic tube 552 provides cost-effective insulation between the leads of both the igniter 551 and the thermocouple 553.

[0037] The response of the flame photometer is related to the relative position D between the end of the sample tube 532 and the gas mixer 518 (at Figure 7F The response of the flame photometer can be changed by adjusting the end position 532E of the sample tube 532. Once the response of the flame photometer is maximized, the optimal position "D" is found.

[0038] like Figure 7F and Figures 10 to 12 As shown, the dimension H1 can be calculated as H1=D+H2+H3, as Fig.7D As shown in Fig.10 Dimension H1 is shown relative to fitting 531. Sample tube 532 is typically pressed into modified fitting 531, thereby allowing dimension H1 to be easily controlled mechanically. In other words, Fig.10 As shown, the optimal position "D" can be achieved by appropriately controlling the dimension H1 of the sample tube assembly.

[0039] exist Fig.11 Dimension H2 is shown for the gas mixer 518. The location of the gas mixer 518 within the combustion chamber body 510 is indicated by the shoulder "A" ( Fig.11 As shown) and the stopper "B" ( Fig.12 The gas mixer 518 is fixed in the combustion chamber body 510 by the external thread 582 engaging with the internal thread in the combustion chamber body 510.

[0040] exist Fig.12 Dimension H3 is shown relative to the combustion chamber body 510 in FIG. 1 . Thus, the optimal position D can be achieved by controlling H1 of the sample tube assembly, H2 of the gas mixer 518, and H3 of the combustion chamber body 510 during manufacturing. This means that the position can be pre-optimized by the manufacturer and therefore does not require any additional optimization by the user. As used herein, "pre-optimization" refers to optimization of the position D performed by the manufacturer or during the manufacture of the system. This is different from, for example, Figure 6B In contrast to the prior art designs shown, Figure 6B The prior art design shown requires user optimization for each system produced. The repeatability of the response between flame photometers is well controlled and the effort to set up the flame photometers is significantly reduced.

[0041] like Fig.12 As shown, the combustion chamber 560 generally includes a curved upper portion 590 that meets a flat lower portion 592 at a rounded portion 594. This semi-circular shape of the combustion chamber 560 is believed to help minimize the physical size of the FPD burner.

[0042] Although the embodiments described thus far generally provide a miniature flame photometer that can be installed in a temperature-controlled furnace of a process gas chromatograph, it is believed that at least some of the embodiments described herein also facilitate easier and less expensive manufacturing. Fig.7D , Fig. 7E and Figure 7F As shown, the combustion chamber body 510 and the gas mixer 518 are designed so that the gas mixer 518 can be assembled from the bottom up.

[0043] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

1. A flame photometric detector for a process gas chromatograph, the flame photometric detector comprising: A combustion chamber body that defines a combustion chamber within the combustion chamber body, wherein the combustion chamber has a generally semi-circular shape; A sample inlet tube configured to introduce a process gas sample into the combustion chamber, wherein the sample inlet tube has an end that is adjustable relative to the combustion chamber; An igniter configured to initiate combustion within the combustion chamber; A thermocouple assembly configured to provide an indication of the temperature within the combustion chamber; and A gas mixer that is threadably disposed within the combustion chamber body, and wherein rotation of the gas mixer affects the adjustable position of the end of the sample inlet tube relative to the combustion chamber.

2. The flame photometric detector according to claim 1, wherein, The combustion chamber has a generally flat bottom.

3. The flame photometric detector according to claim 1, wherein, The igniter and the thermocouple assembly are mounted to a single tube that extends into the combustion chamber.

4. The flame photometric detector according to claim 1, wherein, The adjustable position of the end of the sample inlet tube is pre-optimized for detector response.

5. A process gas chromatograph, comprising: A temperature-controlled oven; At least one chromatographic column disposed within the temperature-controlled oven and configured to receive a sample of a process gas; A flame photometric detector operably coupled to the at least one chromatographic column and disposed within the temperature-controlled oven, the flame photometric detector configured to combust the sample of the process gas and provide an indication of the flame that combusts the sample, wherein the flame photometric detector includes: A combustion chamber body that defines a combustion chamber within the combustion chamber body; A sample inlet tube configured to receive the sample and convey the sample to the combustion chamber, the sample inlet tube having an end that is adjustable relative to the combustion chamber; A gas mixer that is threadably disposed within the combustion chamber body, and wherein rotation of the gas mixer affects the adjustable position of the end of the sample inlet tube relative to the combustion chamber; and A photomultiplier tube assembly coupled to the flame photometric detector and configured to receive an indication from the flame photometric detector and provide a signal indicative of the wavelength of the flame.

6. The process gas chromatograph according to claim 5, wherein, The flame photometric detector is coupled to the photomultiplier tube assembly via an optical fiber cable.

7. The process gas chromatograph according to claim 5, wherein, The flame photometric detector includes an igniter and a thermocouple assembly, and wherein the igniter and the thermocouple assembly enter the combustion chamber of the flame photometric detector via a single orifice.

8. The process gas chromatograph according to claim 7, wherein, the igniter and the thermocouple assembly are mounted to a single tube extending into the combustion chamber.

9. The process gas chromatograph according to claim 8, wherein, the single tube is made of ceramic.

10. The process gas chromatograph according to claim 5, wherein, the flame photometric detector includes an internal combustion emission channel.

11. The process gas chromatograph according to claim 5, wherein, the flame photometric detector includes the combustion chamber having a generally semi-circular shape.

12. The process gas chromatograph according to claim 11, wherein, the combustion chamber has a generally flat bottom.

13. A flame photometric detector for a process gas chromatograph, the flame photometric detector comprising: a combustion chamber body that defines a combustion chamber within the combustion chamber body; a sample inlet tube configured to introduce a process gas sample into the combustion chamber, wherein the sample inlet tube has an end that is adjustable relative to the combustion chamber; an igniter configured to initiate combustion within the combustion chamber; a thermocouple assembly configured to provide an indication of the temperature within the combustion chamber; a gas mixer that is threadably disposed within the combustion chamber body, and wherein rotation of the gas mixer affects the adjustable position of the end of the sample inlet tube relative to the combustion chamber; and wherein the igniter and the thermocouple assembly are mounted to a single tube extending into the combustion chamber.

14. The flame photometric detector according to claim 13, wherein, the single tube is a ceramic tube.

15. The flame photometric detector according to claim 14, wherein, the ceramic tube includes at least four holes axially extending through the ceramic tube.

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