Current collector for combustion oxygen analyzers

Abstract

A combustion oxygen analyzer includes an electronics housing, a probe, and a consumable oxygen cell. The probe is coupled to the electronics housing and is configured to contact a process medium. The probe has a first contact point. The consumable oxygen cell is disposed within the probe and includes a second contact point. The second contact point is urged into contact with the first contact point. One of the first contact point and the second contact point is formed of a curved inconel structure and the other of the first contact point and the second contact point is formed of platinum.

Description

Technical Field

[0001] This invention relates to a combustion oxygen analyzer, and more particularly to a current collector for the combustion oxygen analyzer, as well as wire and pad assemblies. Background Technology

[0002] Industrial processes often rely on energy sources, such as combustion, to generate steam or heat for feeding raw material liquids. Some combustion processes involve the operation of furnaces or boilers. While combustion provides a relatively low-cost energy source, the general goal is to maximize combustion efficiency during the process, as the resulting flue gas leaving the system may be subject to regulations regarding harmful gas emissions. Therefore, one objective of the combustion process management industry is to maximize the combustion efficiency of existing furnaces and boilers, which inherently reduces the generation of greenhouse gases and other harmful byproducts.

[0003] Combustion efficiency can be optimized by maintaining ideal oxygen levels in exhaust gases or flue gases from the combustion process, which ensures the oxidation of combustion byproducts. Field or process analyzers are typically used to monitor, optimize, and / or control the ongoing combustion process. These analyzers typically employ sensors that are heated to relatively high temperatures and operate directly above or near the combustion zone of the furnace or boiler.

[0004] Known process combustion analyzers typically employ a zirconia-based oxygen sensor, positioned at one end of a probe inserted into the flue gas flow. As the exhaust / flue gas flows into the sensor, it diffuses through a filter or diffuser to the vicinity of the zirconia-based oxygen sensor. There is no pump or other flow-inducing device to guide the sample flow into the sensor. Instead, the gas passively permeates the diffuser. The sensor provides an electrical signal relating to the oxygen content present in the flue gas.

[0005] Zirconia-based oxygen sensors provide a potentiometric indication, which is considered a reliable oxygen measurement in a combustion environment, thus allowing for effective and safe process control. Typically, a single probe is inserted into the exhaust stack via process intrusion or insertion. The oxygen (O2) percentage measurement is used to control combustion efficiency in small boilers.

[0006] Typical field analyzers (oxygen sensors with zirconium oxide potential measurement) provide single-point oxygen measurements for controlling combustion efficiency in power plants, incinerators, energy-saving systems, refineries, chemical plants, or small burners.

[0007] As described above, combustion analyzers are used to measure excess oxygen concentration in flue gas stacks. O2 batteries (typically attached to the probe tip) are generally considered the core sensing technology of combustion analyzers. However, O2 batteries are consumables and must be replaced periodically by the end user. When servicing O2 batteries in conventional mountings, the probe frequently suffers irreparable damage to the sensor interface. A technology that provides a solution for industrial combustion analyzers will benefit from this solution, without causing irreparable damage during such replacements. Summary of the Invention

[0008] A combustion oxygen analyzer includes an electronics housing, a probe, and a consumable oxygen cell. The probe is coupled to the electronics housing and configured to contact a process medium. The probe has a first contact point. The consumable oxygen cell is disposed within the probe and includes a second contact point actuated to contact the first contact point. One of the first and second contact points is formed of an Inconel alloy disk, and the other of the first and second contact points is formed of platinum. Attached Figure Description

[0009] Figure 1 This is a schematic view of a combustion oxygen analyzer, and the embodiments described herein can be used with this combustion oxygen analyzer.

[0010] Figure 2 This is an enlarged cross-sectional view of the O2 cell in a combustion oxygen analyzer.

[0011] Figures 3A to 3C The diffusion binding of O2 cells discovered during metallurgical analysis is shown.

[0012] Figure 4A and Figure 4B The new contact pad is shown, which is typically equipped with an O2 sensor for replacement.

[0013] Figure 5 This is a schematic diagram of a welding combustion probe according to an embodiment of the present invention.

[0014] Figure 6A and Figure 6B A wire and pad assembly for a combustion oxygen analyzer according to an embodiment of the present invention is shown.

[0015] Figure 7 The graph shows the impedance data, which is the impedance data of an oxygen sensor using an improved current collector compared to existing current collectors, in air at 736°C, ranging from 100kHz to 0.1Hz.

[0016] Figure 8This is a graph comparing the impedance data of Inconel alloy / platinum interconnects with the impedance data of platinum / platinum interconnects, showing similar impedance performance. Detailed Implementation

[0017] A key design consideration for on-site oxygen analyzers is to reduce the number of spare parts managed by the end user by transitioning to a more robust, permanently sealed design that requires minimal maintenance. One important spare part retained due to its shorter lifespan is the O2 battery, characterized by a zirconia sensor, which typically contacts a platinum pad in a conventional oxygen analyzer to transmit an electrical signal proportional to the oxygen concentration during the process.

[0018] In traditional designs, the platinum pad of an oxygen analyzer and its interface with the zirconia sensor are susceptible to diffusion bonding, which can damage the platinum pad when the O2 battery is removed. Previously, this potential for damage necessitated including a spare platinum pad in the O2 battery spare kit, an undesirable installation for end users due to increased cost and the need for complete disassembly of internal analyzer components. An alternative to the traditional platinum pad design was required to increase the durability of the contact surfaces to survive the many variations in the O2 battery. Following testing, a new interface was developed and implemented to carry the signal from the zirconia sensor without inducing diffusion bonding, thus allowing for a longer analyzer lifespan.

[0019] Figure 1 This is a schematic view of a combustion oxygen analyzer, the embodiments described herein of which can be used in this combustion oxygen analyzer. The combustion oxygen analyzer 100 includes an electronics housing 102 coupled to a probe 104 configured to extend into a process gas source (such as a combustion flue). A flange 106 on the probe 104 is configured to mount the analyzer 100 to a sidewall of the flue. An oxygen sensor (such as...) Figure 2 (As shown) It is usually located near the distal end 108 of the probe 104.

[0020] Figure 2 This is an enlarged cross-sectional view of the distal end 108 of probe 104, showing the replaceable O2 battery. As explained above, the O2 battery 110 is attached to the distal end 108 of probe 104 and is an important component of the analyzer; however, the O2 battery is considered consumable because it must be replaced periodically. Figure 2As can be seen, the O2 battery 110 includes a contact 112 actuated against a permanent pad 114. These two contacts 112, 114 are typically held together by a spring 116 or some other suitable biasing force. During operation, under the force of the spring 116, the permanent contact pad 114 contacts the sensor interface (interface contacts 112, 114), subjecting the probe 104 to elevated temperatures, which can cause diffusion bonding between the two contacts (contacts 112 and 114). Because contact 112 is bonded to the permanent pad 114, this diffusion bonding can damage the permanent pad 114 when the sensor is replaced. It should be noted that this diffusion bonding is caused by sustained pressure, which is the sustained pressure of contacting a precious metal for an extended period at elevated temperatures. Since the contact interfaces of O2 batteries and conventional pads are both made of platinum mesh and maintained under constant mechanical pressure by spring force, a larger contact area can be obtained for diffusion bonding, thereby further enhancing its destructive impact.

[0021] Figures 3A to 3C The diffusion bonding of the O2 cell is illustrated. The image shows the effect of diffusion bonding between contact points and confirms its presence. More specifically, diffusion bonding causes the platinum interface to adhere to the platinum mesh assembly onto the zirconium oxide O2 cell. When this diffusion bonding occurs, replacing the O2 cell becomes quite difficult and time-consuming, resulting in downtime and maintenance difficulties, which can adversely affect the end-user's experience operating their combustion processes. Process shutdown is very expensive and must be passively minimized. To replace the O2 cell, technicians typically remove the probe from the process by removing the flange bolts. The technician will then loosen the diffuser or flame arrester assembly to access the O2 cell. Typically, four hexagonal head screws are removed to detach the O2 cell from the device. A new O2 cell is then inserted into the probe and re-secured using the four screws. Finally, the diffuser or flame arrester is replaced, and the probe is reinstalled back into the customer's process using the flange bolts.

[0022] To mitigate the risk of longer downtime when replacing the O2 sensor, if diffusion bonding occurs, it typically involves replacing the contact pad (e.g., ...) Figure 4A(As shown) and the sensor are replaced. Typically, the wire 120 and pad 122 assembly is not necessary because diffusion bonding has not occurred to the extent that it would damage the permanent pad. In this case, wire 120 and pad 122 are simply discarded. When the conventional platinum mesh does adhere or otherwise suffer sufficient diffusion bonding to damage the permanent pad, replacing the O2 battery is a more complex and expensive process for the end user. In addition to the steps listed above, the technician must replace the internal platinum mesh and wire assembly (which covers the entire length of probe 104). This replacement process can be challenging because the probe is typically mounted high on the flue gas stack. The probe can also reach 12 inches, making this an extremely difficult process if it is not on the ground plane. It may be necessary to remove the probe from the stack and bring it to a service location for a complete replacement. Typically, the technician will begin this process by removing the transmitter from the probe to access the internal support. The internal support is then pulled out of the probe, a difficult task due to the high level of friction along the entire length of the tube. Next, the platinum mesh 122 and wire 120 components are removed from the entire length of the support post and replaced with new components from the O2 battery kit. This can also be a difficult step, as technicians must feed the 12-foot-long wire through a small alumina tube in the center of the support post.

[0023] Figure 4B This is an enlarged view showing an end view of platinum mesh 122, which is typically equipped with an O2 battery replacement kit.

[0024] Figure 5 This is a schematic diagram of a welding combustion probe according to an embodiment of the present invention. To reduce end-user maintenance, a new on-site oxygen analyzer 200 is provided, eliminating the need for any repairs to the probe 204 itself, and ensuring complete welding of the probe 204 in the welding proximity zones 206, 208. As mentioned above, the O2 battery is consumable and is replaced after it is no longer properly calibrated. However, due to the new welding probe design, it is not possible to replace the platinum pad 122 and wire 120 assembly.

[0025] According to the embodiments described herein, a novel solution is provided for the contact point between the consumable O2 battery and the permanent pad of the oxygen analyzer. Diffusion bonding is completely resolved because the contact surface of the permanent pad must undergo many changes within the O2 battery. Typically, the embodiments described herein employ welding probe designs with the use of bent Inconel 625 structures (such as discs, cylinders, or ball and wire assemblies) instead of the permanent platinum pad 114 (e.g., Figure 2(As shown) pairing. By addressing two key properties that contribute to diffusion bonding (material compatibility and degree of contact), this new design significantly simplifies the maintenance process. The bent Inconel alloy structure is a solid, flat surface that contacts the outermost platinum mesh on the O2 sensor. The reduced surface area of ​​this interface and the use of different metals significantly reduce the chance of diffusion bonding, thus achieving the goal of longer product life.

[0026] Figure 6A and Figure 6B A wire and pad assembly for a combustion oxygen analyzer according to an embodiment of the present invention is shown. In addition to increased durability, the Inconel 625 disc, illustrated by reference numeral 302, reduces cost and improves manufacturing efficiency. The disc assembly 300 consists of two parts and a two-step assembly process. First, the tip of the wire 304 is bent to create a larger welding surface and prevent rotation of the assembly 300 when it is mounted into the support. Then, Inconel alloy wire 306 is resistance-welded to the Inconel 625 disc 302, forming a strong joint designed to resist worst-case O2 cell removal forces. The wire and pad assembly 300 is spring-loaded to always be in contact with the sensor. Numerous tests were conducted to validate the performance of the Inconel 625 disc compared to a platinum pad, evaluating key metrics such as system impedance, O2 measurement stability, and signal settling time. All probes were successfully calibrated, generating calibration constants within tolerances, with no discernible differences when using the transmitter or receiving data from the sensor.

[0027] Figure 7 The graph shows the impedance data, which is the impedance data of an oxygen sensor using an improved current collector compared to existing current collectors, in air at 736°C, ranging from 100kHz to 0.1Hz. Figure 7The Nyquist plots are for a fully sensing unit with an Inconel alloy disc / platinum + YSZ / YSZ / platinum + YSZ / Inconel alloy disc and a fully sensing unit with a platinum pad / platinum + YSZ / YSZ / platinum + YSZ / platinum pad in air at 736°C. Note that YSZ is yttrium-stabilized zirconium oxide. The Inconel alloy curve is labeled with reference numeral 350, and the platinum curve with reference numeral 352. The potential difference of the contact resistance was studied by analyzing impedance data (impedance data in air at 736°C ranging from 100kHz to 0.1Hz). This test was performed using a symmetrical unit test setting. It was found that at high frequencies (100kHz), the bulk resistance of the unit with the Inconel alloy disc (7.8Ω) is similar to that of the unit with the platinum pad (7.5Ω) used in conventional probes. This indicates the effectiveness of replacing the platinum pad with an Inconel alloy disk for the purpose of collecting current from the sensing layer. Meanwhile, the polarization resistance (Rp) of the unit with the Inconel alloy disk and the unit with the platinum pad are 44.9Ω and 46.52Ω, respectively. Since Rp is closely related to oxygen sensing performance, replacing the platinum pad with an Inconel alloy disk did not show any impact on oxygen sensing performance.

[0028] Figure 8 This is a graph comparing the impedance data of Inconel alloy / platinum interconnects with the impedance data of platinum / platinum interconnects, showing similar impedance performance. Figure 8 This is a Nyquist plot of the test setup for a symmetrical unit used to collect impedance data. To compare the stability of O2 measurements, two units (one with an Inconel alloy disk (curve 400) and the other with a platinum pad (curve 402)) were run simultaneously for two months. Throughout the test, the unit with the Inconel alloy disk exhibited a similar oxygen reading trend to the unit with the platinum pad, indicating comparable performance between the two. Additionally, the time required for the probe to reach a stable reading was evaluated once powered on. It was observed that at an O2 ambient reading of 21%, the Inconel alloy disk required significantly less time to stabilize, reaching the value within 24 hours, while the platinum pad required approximately two to three days of operation to achieve stability. The shorter stabilization period of the Inconel alloy disk allows for faster calibration of new probes, further reducing downtime for maintenance compared to the platinum pad.

[0029] Although embodiments have been described with reference to Inconel 625 disks, it should be noted that Inconel disks can be pre-oxidized to reduce the impact of chromium deposits on the signal settling period. Finally, sintered Inconel disks can be used, or solid Inconel disks can be EDM-cut to increase porosity and oxygen flow for improved response time.

[0030] Although the invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes in form and detail may be made without departing from the spirit and scope of the invention.

[0031] Cross-reference to related applications

[0032] This application is based on and claims the benefit of U.S. Provisional Patent Application No. 63 / 800,679, filed May 6, 2025, the entire contents of which are incorporated herein by reference.

Claims

1. A combustion oxygen analyzer, comprising: Electronic device housing; A probe, connected to the electronic device housing, configured to contact a process medium, having a first contact point; as well as A consumable oxygen cell is disposed within the probe and has a second contact point that is driven to contact the first contact point. One of the first contact point and the second contact point is formed by a bent Inconel alloy structure, and the other of the first contact point and the second contact point is formed by platinum.

2. The combustion oxygen analyzer as claimed in claim 1, wherein the first contact point is formed by an Inconel alloy disk.

3. The combustion oxygen analyzer as claimed in claim 2, wherein the Inconel alloy disk is formed of Inconel 625.

4. The combustion oxygen analyzer as claimed in claim 2, wherein the second contact point is formed of a platinum mesh.

5. The combustion oxygen analyzer as claimed in claim 1, wherein the first contact point and the second contact point are driven to contact each other.

6. The combustion oxygen analyzer as claimed in claim 5, wherein the first contact point and the second contact point are driven by a spring to contact each other.

7. The combustion oxygen analyzer of claim 1, wherein the electrical connection between the first contact point and the electronics within the transmitter housing is connected to the bent Inconel alloy structure via nickel-based alloy wire.

8. The combustion oxygen analyzer of claim 7, wherein the nickel-based alloy wire is formed of Inconel alloy.

9. The combustion oxygen analyzer of claim 7, wherein the nickel-based alloy wire is welded to the Inconel alloy disk.

10. The combustion oxygen analyzer as claimed in claim 1, wherein the bent Inconel alloy structure is a solid Inconel alloy disk.

11. The combustion oxygen analyzer as claimed in claim 1, wherein the probe is welded.

12. The combustion oxygen analyzer of claim 11, wherein the probe includes a first weld proximity area and a second weld proximity area, the first weld proximity area being close to the consumable oxygen cell and the second weld proximity area being close to the electronic device housing.

13. The combustion oxygen analyzer as claimed in claim 1, wherein the bent Inconel alloy structure is an Inconel alloy disk.

14. The combustion oxygen analyzer as claimed in claim 1, wherein the bent Inconel alloy structure is an Inconel alloy cylinder.

15. The combustion oxygen analyzer as claimed in claim 1, wherein the bent Inconel alloy structure is an Inconel alloy ball.

16. A wire and pad assembly for a combustion oxygen analyzer, the wire and pad assembly comprising: Nickel-based alloy wire; A bent Inconel alloy structure, the bent Inconel alloy being connected to the nickel-based alloy wire, the bent Inconel alloy structure being configured to make electrical contact with a zirconium oxide-based oxygen cell; and The nickel-based alloy wire is configured to extend through the probe of the combustion oxygen analyzer.

17. The wire and pad assembly of claim 16, wherein the wire includes a hook structure near the connection portion. At the connection point, the wire is connected to the bent Inconel alloy structure.

18. The wire and pad assembly of claim 16, wherein the nickel wire is formed of Inconel alloy.

19. The wire and pad assembly of claim 18, wherein the nickel wire is welded to the bent Inconel alloy structure.

20. The wire and pad assembly of claim 16, wherein the nickel wire is resistance welded to the bent Inconel alloy structure.

21. The wire and pad assembly of claim 16, wherein the bent Inconel alloy structure is a solid Inconel alloy disc.

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