By Doug Simmers, Combustion Analyzer Worldwide Product Manager, Emerson Process Management, Rosemount Analytical

Hi! Doug Simmers here. Today, I’d like to talk about flue gas analysis. In the real world, budgets are always tight — personnel and resources are always constrained. It’s critical that plants implement technologies that make plant operation easier, faster, less costly, more compliant, and more efficient. One area where this is crucial is in improving boiler efficiency. Plants with large boilers or industrial furnaces must maintain optimum oxygen levels in flue gases to maximize their boiler efficiency.

AutoCalProbeTo ensure that flue gas oxygen levels are always accurate, the new Rosemount Analytical 6888 oxygen probe from Emerson now offers an online “calibration recommended” diagnostic which tells plant personnel that a given oxygen probe needs to be calibrated.

Calibration solenoids mounted inside the probe head make calibrations easier than ever, without requiring a technician to visit the analyzer. It also eliminates the cost of installing and wiring a separate solenoid box. The calibration recommended diagnostic also removes the need to conduct calibrations on a schedule. eliminating many scheduled calibrations that are actually unnecessary.

6888_see_thruThere are several new diagnostics available in today’s advanced oxygen probe technology, including a “plugged diffuser/filter” alarm for applications that have fly ash or other particulate entrained in the flue gases. Also, a “stoichiometer” feature indicates the level of reducing conditions if the oxygen readings go to zero percent. In addition, an elevated temperature capability for furnaces that operate at very high temperatures is also a feature that’s available and should be considered. These new diagnostics permit operators to run boilers and furnaces with confidence that the best efficiency is being maintained without compromising safety.

Advanced diagnostics and automatic calibration improve accuracy in flue gas analysis which is crucial not only because it provides better combustion efficiency, but also because it minimizes the production of greenhouse gases such as CO2 and 530thermal NOx, improving plant compliance with environmental regulations.

Get more information on advances in flue gas oxygen analyzers or watch our video on efficiency and cost-savings in flue gas analysis.

What kinds of flue gas oxygen analysis challenges are facing your plant? Can new technologies improve your boiler efficiency and keep you off the stack?

Author: Greg Latch, Emerson Process Management, Rosemount Analytical

Here at Rosemount Analytical, we’ve got a very exciting project we’ve been working on for an Asia Pacific customer. This story is significant if you want to use gas chromatographs in your operation, but lack the communications wiring and infrastructure to get the information and diagnostics back to your control room where you need them.

In this case study, the customer is a gas distribution and pipeline company in Asia Pacific. They offer clients a seamless service capability across 30 receipt points and 100 delivery points.  Each of these points have either existing gas quality/metering stations, the potential for upgrading stations, or the potential for new additional points to manage gas quality and transfer measurement.

The company’s driving need was to monitor the gas composition to manage the feed to downstream LNG plants. They needed to offset the risk of trace heavy hydrocarbons (that freeze in the liquefaction process) and/or unacceptable trace sulphur levels that would severely impact the downstream processes to improve overall plant efficiency and avoid penalties caused by no or low non-LNG products (NGLs, condensates).

To achieve the required low detection limits of gas composition, the Emerson team had to complete comprehensive laboratory pre-testing/pre-work to prove that we could measure to these ppb trace levels in the client’s gas stream.

Trace Heavies (FID)                        Detection Limit (ppb)

  1. C6+                                                      20ppb
  2. Neopentane                                          20ppb
  3. C9+                                                      20ppb
  4. n-Hexane                                             20ppb
  5. C8                                                        20ppb
  6. Benzene                                                20ppb
  7. Cyclohexane                                         20ppb
  8. n-Heptane                                            20ppb

Trace Sulphur(s) (FPD)                   Detection Limit (ppb)

  1. Hydrogen Sulphide                                50ppb
  2. Carbonyl Sulphide                               100ppb
  3. Ethyl-Mercaptan                                  100ppb
  4. Methyl-Mercaptan                               100ppb
  5. Total Sulphur (Calculated)                   100ppb

Once that hurdle was behind us, the real challenges of communications requirements for the customer began. Standard RS485 Serial Modbus communications are generally used for control and measurement readings of gas composition — normally easily achieved for long plant distances of more than 100 meters. However, the rich diagnostics from the gas chromatograph requires management and interpretation to be performed over higher-speed Ethernet connections — communications not reliable for distances greater than 100 meters. To facilitate the long-distance communications necessary, two creative solutions were identified.

The 700XA gas chromatograph uses MON2020 software that requires Ethernet connection to fully utilize the data-rich configuration and diagnostic capabilities. In our first option, we solved the distance problem by engineering a local Wi-Fi-Ethernet solution for the plant from the safe area of the control room or motor control room to the hazardous area of the gas chromatograph shed, enabling access to the GC Ethernet ports for MON2020 support. On top of this site local Wi-Fi network, a cellular-Ethernet network access point from the plant control room to offsite/remote client and Emerson offices was created for future support if required. With the availability of remote access via the above wireless configuration, the user can troubleshoot the GC remotely. They can analyze and understand the problem with the GC, gain access to it remotely in all weather conditions, and prepare the parts to take for replacement where needed before actually dispatching the technician out to the field. Certain problems could be solved by remotely validating the GC and its performance. This eliminates the need to have the technician go to the site whenever there seemed to be some trouble, and allows for the technician to spend his time on other more areas in the plant to increase his productivity.

RAI_IMG_WirelessGC-BlogThe alternative option was to run fibre optics for communications into each gas chromatograph shelter for remote diagnostic and maintenance access from the MCC/control room. This method would have increased implementation time and financial impact dramatically (over 5x!), so the former option was chosen.

The figure to the right shows the option of remote Wi-Fi-Ethernet solution as well as the Cellular-Ethernet solution the plant implemented. For this customer, the Emerson 700XA gas chromatograph with this unique communication solution provided:

  • Precise detection of gas composition with minimum field site exposure time in hazardous areas
  • Easy maintenance through local and remote access via Ethernet
  • Highly flexible and expandable communications network
  • Cost savings of $300,000 to $400,000 over alternate solution

Have you implemented a wireless solution in your process? Tell us about your challenges and successes in comments below.

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