Large, complex fireboxes in world-scale steam methane reformers (SMR) represent safety challenges such as personnel safety while interfacing.
Furnace protection is important from a business asset perspective since this equipment represents about 35% of the total hydrogen plant asset value. However, an even more important consideration is personnel safety while interfacing with the firebox during the startup and light-off of hundreds of burners. Safety is also an issue during intermittent manual monitoring and data collection.
Therefore, hydrogen producers are faced with a decision to sacrifice firebox data acquisition to reduce hazard exposure. Extrapolation and leveraging of a limited amount of firebox data is the result of the decision. This extrapolation of limited data is typically historical based, as is the operation and maintenance of the firebox. Notable firebox failures occur from gaps in historical knowledge.
In response to these and other challenges, Chevron chose Topsoe Furnace Manager (TFM) technology to ensure safe and reliable commissioning, startup and operation of their two new world-scale hydrogen plants in 2018. From the initial burner lighting of the first steam methane reformer (SMR) up through normal operation of both hydrogen plants, TFM successfully monitored firebox conditions without incident or issues.
Chevron wanted to minimize human interaction with the furnace firebox to increase personnel safety. In addition, they explored several technical considerations, including extent of coverage of the firebox by operators looking into viewport windows, including fire-box data collection, duration of firebox surveillance, and evaluation of results of burner or process adjustments.
TFM was identified as the optimal technology to reduce human interaction with the firebox and provide more persistent coverage of the firebox than short intervals (less than one minute) of “eyeball viewing” through viewports.
Even under the best of circumstances, manual fire-box interaction is typically relatively short, with only about 1000 hours or less of data collection annually. TFM collects millions of data points annually, including burner and catalyst tube temperatures, deviation alarms and pictures, and can be accessed remotely by the organization outside of the plant. The data are stored in an easy-to-use historian for future reference.
During the initial light-off of the first SMR, flame detection by installed flame scanners was intermittent. Reliable flame detection is essential to prevent a furnace “bogging” (fuel rich) event. Traditional flame scanners typically experience loss of signal, especially on the initial burner light-off before they are properly adjusted and positioned. In this situation, TFM provided a reliable second source of flame detection during the critical first burner lighting phase.
Topsoe Furnace Manager captured the first SMR burner light-off – a situation that is often missed by traditional flame scanners due to loss of signal.
Burner lighting and heat up
TFM continued to capture images as burner lighting continued throughout the initial heat-up period. This quick view of all burners during the light-off period allowed the Asset Owner to direct and organize operator actions to achieve an optimal process. The ongoing monitoring by TFM ensured that all burners were lit, had sufficient air to avoid afterburning, and that flames were not impinging upon catalyst tubes in the SMR at any time.
With continual TFM burner monitoring, operators were freed to complete other important tasks in the plant, minimizing their ascent to the top of the SMR for burner and combustion air valve adjustments. The reduction of human-firebox interaction allows personnel to perform higher value work, such as image and data analysis, collaboration, and/or minor maintenance and turnaround planning.
It is crucial to safety to understand the condition of the firebox during a plant try-out. With TFM, the firebox can still be “seen” with images of the firebox’ heat radiation even when burners have tripped offline. This information confirms that the plant’s burner management system is active and has safely shut off fuel and flames.
TFM captures the subtleties of burner heat signatures, especially important at high temperatures. Without proper burner heat signatures, the mechanical reliability of the burners can degrade along with heat release and overall burner performance.
Topsoe Furnace Manager produces a detailed picture of burner heat signatures that helps maintain burner performance.
Monitoring under normal operation
After transitioning to normal operation with pressure swing adsorption (PSA) off gas fed as fuel to the SMR firebox, TFM’s movement functionality was utilized to physically view the lower part of the catalyst tubes operating at higher temperatures than the section near the burners.
When in normal operation, plant rates were increased while adjusting various operating parameters such as steam-to-carbon (S/C) ratio and operating temperatures to begin the optimization process. Catalyst tube temperatures are an essential input in this phase, and TFM’s tube temperature correlation was utilized, based on historic images checked with pyrometer readings at specific locations at specific times.
The first step in the process of correlating tube temperatures is to fully understand the characteristics of each firebox. Topsoe’s experience in firebox monitoring based on many years of collecting tube temperature data on all types of SMR’s was leveraged to TFM’s tube temperature correlation process.
For Chevron’s SMR fireboxes, tube temperatures were very consistent from the beginning. Burner impingement was not observed, and burners did not require significant adjustments. Process blockage or other process-related problems were not significant. TFM regions-of-interest were established based on the observed temperatures in specific areas of the catalyst tube banks. Alarm settings were established in discussions with Chevron to provide an early warning notification about hot tubes.
Topsoe worked closely with Chevron to “fingerprint” the tube temperature profile of both SMR’s at normal operating conditions. Individual temperature charts and graphs were created to assist Chevron in quickly evaluating tube temperature deviations whenever they developed.
Multiple plant firebox monitoring
Another important requirement for Chevron was to have the ability to manage both H2 plants, including both large SMR’s, from a single console with one operator using technology for monitoring. TFM provides the imagery for continuous monitoring of both fireboxes.
TFM displays were set up so that both SMR’s were monitored continuously in immediate proximity to the plant’s DCS control system. Any firebox upsets or changes required are observed and will be in alarm if outside of normal operating range. In this fashion, TFM provides great insight into firebox condition prior to dispatching an operator to the field to inspect and hunt for a problem by opening viewports.
Topsoe Furnace Manager allows a single operator to monitor several fireboxes at once, including burner and catalyst tube temperatures.