Integrated System of Analyzers
The C5A analyzer, the trial analyzer used to monitor incoming lignite fed on conveyer C5A, was installed in August 2006 on a six-month trial lease. Initially, the analyzer was calibrated using known static samples from the mine. The calibration part of the overall installation/commissioning process took about six weeks. Although operation began with a preliminary calibration (based on a very limited data set), the unit quickly began to be a useful trending device. The operators in the control room began watching the ash trend charts and quickly learned to adjust the fuel supply when ash content went out of spec.
Once the unit was operating, additional dynamic comparative data samples were acquired using the existing sweep-arm mechanical sampler on the C5 belts (Figure 7). Given the number of seams and the large number of possible combinations of lignite supply, it took several weeks to collect sufficient data to complete a robust system calibration. During this initial performance optimization period, SABIA configured its systems to provide a data stream directly into the mine’s existing data management system with the purpose of providing the trend data stream directly to those mining the coal. More on that development later.
7. Looking at lignite. The coal feed moves from left to right down the conveyor. A belt scale collects information to make a coal thickness correction. Next, a manual sweep arm collects samples for lab comparisons. Finally, a SABIA PGNA sampler is installed on the conveyor that supplies fuel to the boiler. Courtesy: SABIA
The C5A and C5B analyzers monitor the lignite flow to the two boilers. The two silos are loaded such that Silo 1 is less than 15% ash lignite and Silo 2 is less than 20% ash. The control room operators have the ability to make limited adjustments to the blend ratio depending on the real-time trend data from the analyzers. The plant has four day silos for each boiler. With full day silos at full burn rate, this represents about 5 to 6 hours of fuel. Prior to commissioning the analyzers, any fuel quality issues would fill the day silos with 6 or more hours of bad fuel before operators could divert the nonspec fuels. Today, the analyzers allow the operators to make preemptive changes to avoid the fuel problems before they appear in the boilers.
The C2 analyzer also plays a key role in the fuel supply operation. Data from the C2 analyzer is used in real time to make mining modifications that have a material result on the quality of the lignite going into the silos. The C2 analyzer data is available on the Red Hills Mine intranet because all the SABIA analyzers are web browser – based machines with separate IP addresses.
Red Hills Mine uses its wireless network in the open-pit mine so all the real-time information from the analyzer is available to the mining operation. A wireless router in the main mining office is linked to a Motorola mesh wireless network in the pit. Panasonic Tuffbook laptops with swivel displays were mounted in key vehicles used in the mine. Another laptop was mounted in the Easi-Miner (Figure 8), one in the Caterpillar 5230 backhoe, and one in the pickup of the shift supervisor. Together, the analyzer can display running average results displayed on a 5-minute, 10-minute, 40-minute, and 4-hour basis. The mine operators are typically making decisions on the 10- and 40-minute results.
8. Wealth of shared data. A Panasonic Tuffbook laptop was mounted in the Easi-Miner (shown), in the Caterpillar 5230 backhoe, and in the pickup of the shift supervisor. The analyzer can display running average results on a 5-minute, 10-minute, 40-minute, and 4-hour basis. The operators typically are making decisions on the 10- and 40-minute results. Courtesy: SABIA
The lignite haul operation focuses on two tasks: maximizing seam recovery and ensuring a consistent product is delivered to the fuel storage silos. Working with shallow/rolling seams or unexpected changes in seam quality can be extremely challenging. The C2 analyzer has become a key part of the mining operation with two fundamental control actions available to ensure that the lignite delivered to the two fuel storage silos meets the low- and high-ash constraints.
For the loading machine (either the Easi-Miner or 5230 backhoe), the operator simply adjusts his mining depth if the analyzer shows that the lignite being mined is too far beyond the target quality. If the operator is certain he is in seam but that the lignite is simply of a quality beyond the acceptable target, another loader swings into action, taking fuel from one of two divergent good-quality fuel stockpiles kept in the mine area. This loader provides alternate loads to a truck from the stockpile that is delivered to the power plant’s truck dump. In this way, the average lignite delivered to the fuel storage silos meets the quality target, resulting in much more uniform lignite quality delivered to the boilers. Via radio, the shift supervisor orchestrates the process, responding to trend data from the analyzer.
Red Hills Mine and Red Hills Power Plant have learned how to coordinate their actions based on trend data collected from a PGNA coal analyzer to ensure that only quality coal is fed to the CFBs. Today, the power plant has not only eliminated out-of-spec fuel ash – caused unplanned shutdowns, but it also has significantly reduced "derated" operational periods. The mine is now consistently delivering fuel that optimizes boiler operation and extends the period between scheduled outages, both of which add profit to the bottom line for both companies.
—Steve Foster (sfoster@sabiainc.com) is executive vice president of SABIA Inc. Bob Halsell is technical coordinator at the Red Hills Mine of North American Coal.
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