Siemens LDS6 is working to put minds at ease at the Tasmanian Electro Metallurgical Company (TEMCO), a subsidiary of BHP Billiton, by enabling the manganese ferroalloy plant to alert its workers of imminent furnace explosions in time to prevent them.
TEMCO supplies its steel additive to more than 50 companies around the world. With its four electric arc furnaces, TEMCO can produce more than 250,000 tonnes of manganese alloys per year, 80 percent of which is exported.
“Sudden explosions are known to arise in these furnaces due to the temperature-control mechanism, which pumps water through a series of tubes inside the furnace to maintain the internal temperature,” said Paul Dennis, process technology supervisor at TEMCO. “Over time, the water eventually erodes these steel tubes, and this allows some water to leak into the furnace.”
According to TEMCO, the high furnace temperatures and increasing water leakage are the main causes of the sudden explosions. At 400°C to 600°C, the water that enters the furnace through the eroded steel tubes is converted into steam. As this erosion continues and causes more steam to accumulate inside the furnace, the internal pressure builds up until it eventually explodes.
The Siemens LDS6 laser gas analyzer allows for accurate and high-speed monitoring of gas composition in a variety of applications. Benefits of the LDS6 gas analyser include instant response; calibration is not necessary; maintenance needs are kept at a minimum; and it is designed to work in high temperatures, high levels of dust, and high moisture environments.
Brendan Welsh, Siemens product manager, said that because this was the first time the LDS6 was used in submerged arc furnaces on a global scale, caution had to be taken in order to guarantee its accuracy, sensitivity, reproducibility, reliability, and maintainability.
“One of the major modifications required for this application was to counteract the extremely high levels of dust present at the facility,” Welsh said. “Around 100 grams of dust per cubic metre was recorded, which was much too high for the laser analyser to work accurately.
“Siemens modified the analyser specifically to address this challenge,” Welsh continued, adding that Siemens manufacturers in Germany, as well as the Australian-based Siemens reseller and BHP Billiton developed a suitable analyser.
“We built an air chamber that’s used to blow the dust off the laser every few minutes. This allows the laser to gain an accurate scan of the water levels and consequently, delivers consistent and reliable readings.
“Trials undertaken by Paul Dennis enabled a set of control limits to be established, with the analyser detecting water leaks several hours before any other traditional methods have been able to. These limits are used to foreworn of any future explosions, so that plant workers can take the appropriate safety measures, including shutting down the facility if needed.”
Siemens said the initial trial of the LDS6 in TEMCO submerged arc furnace showed promising results. Small leaks in the furnace, which have traditionally been undetected, were now able to be monitored, with 100 percent accuracy.
Using this analyser, Dennis was able to monitor water level trends. In one case, he said he noticed abnormally high increases in the furnace’s water levels and consequently ordered a shut down of the furnace.
Despite the costs involved in shutting down the furnace, Dennis said further examination after the fact showed that an explosion was likely to happen within the next two hours if nothing had been done.
The information collected from this trial has helped establish a set of control limits that will be used to foreworn of any future explosions.
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