Ignition aid for flame ionization detectors

Abstract

A method and apparatus for an ignition aid for a flame ionization detector, comprising a body that crosses the detector chimney to create turbulence in the gas flow exiting the detector to enhance mixing of the fuel / air mixture with the ignition source when the ignition source is activated.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. patent application Ser. No. 18 / 093,556, filed Jan. 5, 2023. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable. Names of the parties to the joint research agreement

[0003] Not applicable. Reference to a compact disc appendix to a sequence listing, table, or computer program listing

[0004] Not applicable. Statement of Prior Disclosure by Inventor or Co-Inventors

[0005] Not applicable.

[0006] The present invention relates to a flame ionization detector ignition aid for use in gas chromatography, which requires an ignition source to start the flame that provides the detector signal. The present invention is designed, in both an apparatus and a method, to increase the likelihood that the flame will be ignited when the detector initiates the flame start procedure. [Background technology]

[0007] There are numerous references describing the gas chromatography (GC) process. Flame ionization detectors (FIDs) are widely used in gas chromatography to convert compounds eluting from the gas chromatograph column into an electrical signal suitable for recording. Flame ionization detectors are commonly used GC detectors due to their linearity, sensitivity, and response to hydrocarbons. Flame ionization detectors are based on a hydrogen / air flame that combusts hydrocarbons as they elute from the chromatography column. The hydrocarbon combustion process produces ions and electrons in the flame, measured with a picoammeter, which can be recorded for further evaluation.

[0008] To start a flame in an FID, manufacturers utilize an ignition source, such as a glow plug, to provide an initial source of flame ignition. In at least one case, the igniter is screwed into the side of the detector until it is fully seated against a brass O-ring that contacts the side of the detector's chimney (also known as a castle). When an operator wants to ignite the detector, or when the instrument senses the detector's flame has gone out, a signal is sent to the glow plug igniter, turning it on. Additionally, in at least one case, the detector's flow rate is increased to create a rich fuel / air mixture to enhance the ignition process. These steps are performed to ignite or reignite the flame in the FID. Summary of the Invention [Problem to be solved by the invention]

[0009] In many cases, this is insufficient to ignite the flame. Therefore, a useful procedure for assisting FID flame ignition is to supply a low flow of air over the top of the detector chimney to create turbulence within the chimney to enhance mixing of the fuel gas with the hot glow plug. Currently, this process is performed by an operator standing at the instrument and supplying a puff of air over the top of the detector chimney. Having to provide this type of reinforcement to assist flame ignition has significant drawbacks. First, when the instrument initiates the ignition procedure, the operator must be present to reignite the flame. If the flame goes out overnight while the instrument is operating unattended, the automatic reignition procedure is often not successful, resulting in an unbalanced analysis. Additionally, while it is possible to safely supply a low flow of air over the detector chimney, the ignition process may ignite in such a way that the flame exits the chimney area. If the operator is not careful to avoid this ignition flame, the operator could be burned by the ignition process, especially if they are present above the chimney. Finally, in actual operation, when it is difficult to guarantee that the flame will auto-ignite, many laboratories have been known to leave unused detectors lit, resulting in the detectors igniting when they need to switch to an unused channel. The need to keep detectors lit means that the instrument is consuming gas (hydrogen and air) while that channel is not in use, simply to ensure that the flame will ignite when the channel needs to be used. [Means for solving the problem]

[0010] The present invention provides an ignition aid device for a flame ionization detector, comprising a body that traverses the detector's chimney to generate turbulence in the gas flow exiting the detector when the ignition source is activated to enhance mixing of the fuel / air mixture with the ignition source. In one embodiment, the device further comprises one or more bolts and / or rods connected to the body. Preferably, at least a portion of the rod is threaded, and the rod extends from the exterior of the body to the interior of the body. The body is preferably hollow and most preferably comprises at least two sections having different interior dimensions. The body can remain in place except when it is necessary to measure flow rates or perform maintenance on the detector. The device does not require operator intervention to enhance flame ignition accuracy, does not modify the chimney in a way that interferes with the detector's existing function, and does not require additional pneumatic or electronic equipment to be installed in the detector.

[0011] The present invention also provides a method for increasing the likelihood of ignition in a flame ionization detector, comprising providing a body within the detector chimney to disrupt flow near an ignition source of the flame ionization detector, thereby ensuring ignition of a flame within the detector when the igniter is activated. In one embodiment, the disrupting step is performed automatically. The body preferably further comprises one or more bolts and / or rods connected to the body. Preferably, at least a portion of the rod is threaded, and the rod extends from the exterior of the body to the interior of the body. The body is preferably hollow and most preferably comprises at least two sections having different interior dimensions.

[0012] Further scope of the applicability of the present invention will be set forth in part in the following detailed description taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

[0013] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the invention and are not to be construed as limiting the invention. The drawings are as follows: [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a prior art example of a flame ionization detector that uses a glow plug in the flame ionization detector chimney to ignite the flame.

[0015] [Figure 2] 3 shows a variant of the chimney according to the invention;

[0016] [Figure 3] Zoomed-in view of the detector signal when the column effluent is split equally between the detector without and with the ignition aid, demonstrating that the detector aid does not significantly affect the detector noise level.

[0017] [Figure 4] Chromatograms of the detector signal for a hydrocarbon sample injection when the column effluent is split equally between the detector without and with the ignition aid, demonstrating that the detector aid does not significantly affect the detector response to hydrocarbons. DETAILED DESCRIPTION OF THE INVENTION

[0018] To eliminate the need for manual intervention and increase the reliability of auto-ignition in igniting an FID flame, the present invention provides a means for consistently directing at least a portion of the fuel / air mixture toward the glow plug. The present invention creates turbulence in the fuel / air mixture in the region of the glow plug, making ignition substantially more reliable without operator intervention. This enhancement is provided by placing a partial obstruction in the fuel / air path adjacent to the glow plug. With the present invention, ignition or re-ignition is much more reliable, significantly reducing the need for operator intervention.

[0019] Figure 1 shows an example of a prior art flame ionization detector. The gas chromatography process is described in the provided references. Briefly, in a gas chromatograph, carrier gas 10 coming from a chromatography column 11 is directed to a detector, typically located in the top wall 15 of a chromatography oven. Upon reaching the detector, the carrier stream is combined with fuel gas (hydrogen) 12 and transported through a small orifice known as a jet 13 into the detector's main chamber. In the main detector chamber, the hydrogen / carrier gas mixture is mixed with air 14, which is supplied to the detector's base, and flows through a detector collector 16, insulated from the detector's main body by insulator 15. During operation, a flame exists at the jet's exhaust tip. This flame destroys hydrocarbon compounds, producing ions and electrons that can be amplified by a picoammeter (not shown) to generate an analytical signal. The flame, once ignited, is typically self-sustaining at the tip of the jet.

[0020] To initiate the flame that forms the basis of a flame ionization detector, the carrier / fuel / air mixture is exposed to an ignition source, such as an energized glow plug 33 that is typically screwed into the wall of the chimney 30. During ignition, the glow plug provides initial energy to the carrier / fuel / air mixture for ignition. The glow plug is switched on 32 and energized by a voltage source 31. As noted above, once ignition is achieved, the flame is typically self-sustaining and the glow plug is typically turned off.

[0021] As shown in Figure 1, the glow plug is slightly recessed from the inside diameter of the chimney and is mounted above the collector. The advantage of having the ignition source above the collector is that there are no flow disturbances near the collector, which can be a source of detector noise. However, if the flow up the chimney is not turbulent, the electrons emitted from the glow plug may not interact sufficiently with the fuel / air mixture to start a flame when the glow plug is turned on. To improve the likelihood of ignition, the flow rate is sometimes increased to create a rich fuel / air mixture in an attempt to increase the probability of ignition.

[0022] The chimney on this type of FID is held in place by a threaded collar 17 that screws onto the base of the detector. This allows the chimney to be removed to access the jet for repairs if necessary.

[0023] FIG. 2 shows the ignition aid described in this patent. The detector remains largely unchanged. Adjacent to the glow plug, a bolt or rod 50 threads into the chimney and is positioned proximal to the end of the glow plug. This bolt creates a sufficient perturbation in the detector gas flow so that, when the flame-ignition sequence is triggered, a portion of the fuel / air mixture is substantially more likely to interact with the electrons emitted from the glow plug and start the flame. The use of a threaded bolt allows an operator to easily remove the bolt if they need to measure the flow rate in the chimney using current technology, yet still be able to replace the bolt. Additionally, the threaded bolt allows an operator to remove the bolt to slide a threaded collar up or down the chimney as needed for maintenance.

[0024] Note that the ignition aid is located well above the detector collector, so the turbulence generated by this aid does not significantly affect the detector noise. This is demonstrated in Figure 3. The end of the analytical column was split with a T-junction, and the exhaust from the column was transferred approximately equally between detector 60, which does not have an ignition aid, and detector 61, which does have an ignition aid. The two signals yield substantially the same noise level between the two detectors.

[0025] It should also be noted that the position of the ignition aid is located above the collector where the signal is acquired, so the ignition aid does not significantly affect the sensitivity of the detector and therefore does not interfere with normal operation of the detector. This is demonstrated in FIG. 4. Using the same configuration as in FIG. 3, a sample containing two hydrocarbon species was injected onto the column. The top trace 65 is a chromatogram of the hydrocarbon mixture eluting through the FID without the ignition aid, and the bottom chromatogram 66 is a chromatogram of the same mixture eluting through the FID with the ignition aid. The two signals yield substantially the same response levels between the two detectors.

[0026] For example, a key advantage of ignition aids, as opposed to moving a glow plug in line with the fuel gas, is that the bolts are not adversely affected by moisture generated by the hydrogen / air flame, while rusting glow plugs render them inoperable. Furthermore, ignition aids do not require additional wiring and do not require the glow plug to be moved from its original position, which could change the circuit resistance and introduce errors into the glow plug electrical circuit. Finally, the balance between detector structure and operation is not significantly altered by ignition aids.

[0027] To evaluate the effectiveness of the ignition aid, 10 consecutive ignitions were conducted at 5-minute intervals for a detector without a front aid (prior art) and a detector with a rear aid. The flow settings (30 mL hydrogen / 300 mL air) were the same for both detectors, and each detector was at 220 degrees Celsius. Table 1 below shows the results of 10 ignition cycles with and without the ignition aid. No additional low flow rate over the top was provided for any of the ignition cycles, with or without the ignition aid. All ignition cycles in the table utilized increasing flow rates for the detector. It is clear that the success of the ignition cycle is substantially increased for the detector with the ignition aid.

[0028] The forward detector (prior art) was then instructed to ignite five times with the aid of an airflow over the top provided by the technician, and ignited all five times, demonstrating that the detector had no underlying defects.

[0029] The experiment was repeated with a detector temperature of 250 degrees Celsius and a flow rate of 35 mL of hydrogen and 350 mL of air. The results were identical: zero ignitions over 10 trials for the detector without the ignition aid, and 10 ignitions over 10 trials for the detector with the ignition aid. The only difference between the two experiments was that the average signal for the detector with the aid was 12.1 due to the higher airflow through the detector.

[0030] Several locations on the radius of the chimney were tried, but no change was found in the effectiveness of the ignition aid of the present invention, as long as the ignition aid terminated near the igniter. JPEG2026501459000002.jpg136158

[0031] Although the present invention has been described in detail with particular reference to these preferred embodiments, other embodiments may achieve the same results. Variations and modifications of the present invention will be apparent to those skilled in the art, and it is intended to cover all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above and / or in the accompanying documents, and of the corresponding applications, are hereby incorporated by reference.

Claims

1. 1. An ignition aid apparatus for a flame ionization detector, the apparatus comprising: a body that traverses the detector chimney to create turbulence in the gas flow exiting the detector to enhance mixing of a fuel / air mixture with the ignition source when the ignition source is activated.

2. The device of claim 1 , further comprising one or more bolts and / or rods connected to the body.

3. The device of claim 2 , wherein at least a portion of the rod is threaded.

4. The device of claim 2 , wherein the rod extends from an exterior of the body to an interior of the body.

5. The device of claim 1 , wherein the body is hollow.

6. The device of claim 5 , wherein the body comprises at least two sections having different internal dimensions.

7. 10. The device of claim 1, wherein the body can remain in place except when needed to measure flow or perform maintenance on the detector.

8. 10. The apparatus of claim 1, wherein no operator intervention is required to increase the likelihood of igniting the flame.

9. 10. The apparatus of claim 1, wherein the chimney is not modified in a manner that interferes with the existing function of the detector.

10. 10. The device of claim 1, wherein the detector does not require additional pneumatic or electronic equipment to be installed.

11. 1. A method for increasing the likelihood of ignition in a flame ionization detector, comprising: providing a body within the detector chimney; disrupting a flow adjacent an ignition source of the flame ionization detector; thereby ensuring ignition of a flame within said detector when the igniter is activated; A method comprising:

12. The method of claim 11 , wherein the disturbing step is performed automatically.

13. The method of claim 11 , wherein the body further comprises one or more of a bolt and / or a rod connected to the body.

14. The method of claim 13 , wherein at least a portion of the rod is threaded.

15. The method of claim 13 , wherein the rod extends from an exterior of the body to an interior of the body.

16. The method of claim 11 , wherein the body is hollow.

17. The method of claim 16 , wherein the body comprises at least two sections having different internal dimensions.

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