Hatch fibre optic technology advances furnace temperature mapping
Consulting engineering and project implementation firm Hatch has developed a Tapblock Fibre Optic Temperature Measurement System, which makes use of fibre optic sensing technology to measure temperatures on the hot face of copper coolers and in the tapping channel of a water-cooled matte tapblock.
Hatch Global Director of Control Technologies, Terry Gerritsen, says that the Tapblock Fibre Optic Measurement System provides accurate temperature readings from previously inaccessible locations inside a furnace. The temperature measurement system is currently being used on several furnaces in South Africa and Australia, and will soon be in use in Canada.
“On most applications, the fibre optic sensors and associated basic monitoring software provide data from areas of the tapblock that have never before been accurately measured on an operating furnace. Compared to thermocouples, which have traditionally been used, the fibre optic sensors provide superior temperature measurements, in terms of accuracy, multi-position measurement density and the ability to install them in different locations,” explains Gerritsen.
The Tapblock Fibre Optic Measurement System’s ability to obtain dense multi-position temperature coverage on the hot-face of copper coolers and tapblocks was not previously achievable. Gerritsen says that this important advancement allows the operator to gain continuous feedback on refractory condition as increasing temperatures are indicative of refractory degradation.
Key features
When the optical fibre sensor technology was first discovered in the 1990s, scientists and engineers realised that by strategically introducing ‘defects’ or ‘sensors’ into the fibre, light transmitted down the length of the fibre would partially be reflected back. “By analysing the light that is reflected back, one can establish the temperature at each of the sensor points,” says Gerritsen.
In addition to the temperature range, a key consideration is the small size of the fibre optic sensor cable. A single optical fibre - including protective cladding and buffer layers - is only about the same diameter as a strand of human hair, a couple of hundred microns. The actual length of the optical fibre varies depending on application, while the number of sensors varies depending on the density of mapping required.
The size of the optical fibre allows for complete temperature mapping, which in turn allows plant engineers to accurately predict when a controlled shutdown will be necessary, thus resulting in greater efficiencies both in terms of costs and timing. “Having to shutdown a furnace a few days early could equate to millions of rands. Predictability is a key issue here in that the Tapblock Fibre Optic Temperature Measurement System allows one to detect the advance of refractory damage much sooner than has been possible with thermocouples. You can see problems developing several weeks in advance,” says Gerritsen.
A further disadvantage of using thermocouples is that there are a limited number of sensors/measurements possible due to their large size in spatially confined applications. This in turn doesn’t allow for an accurate temperature reading of the entire tapblock. Readings taken from a thermocouple could indicate that the tapblock is functioning as it should be, when in fact, it could be in danger of failing in unmeasured areas.
Gerritsen notes that in quantities greater than about 100, the cost difference between a fibre optic sensor and a thermocouple is negligible. “Ultimately, it is a negligible cost to the client when compared to having to shut down early or wait too long for the furnace to shut down itself and suffer damage,” he adds.
Meanwhile, Gerritsen points out that the surface temperature map (data received from the sensors), enables the detection of refractory loss and is monitored and analysed by hand and by software that is currently under development. “The aim is for computers to assist with the evaluation using software that should be ready for use in several years,” explains Gerritsen.
Gerritsen, who has been with Hatch for more than 20 years, is the Director of the Control Technologies Group at Hatch Canada’s Mississauga office. He explains that the Control Technologies Group falls under the Technologies Division within Hatch.
“It is somewhat different to the consulting engineering function of Hatch in that the Control Technologies Group delivers Hatch products. We specialise in process control systems including the design and supply of control technology for Hatch furnaces. The control technology is also available as a retrofit to other furnaces. The Tapblock Fibre Optic Measurement System is a smelter differentiator technology for Hatch,” says Gerritsen.
Hatch is currently looking to establish a Control Technologies Group in South Africa in order to build capacity locally. The Hatch Africa Control Technologies Group is headed by Warren Braun, Manager of Control Technologies Africa.
Ends.
Notes to the Editor
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About Hatch
Hatch supplies process and business consulting, information technology, engineering, and project and construction management to the mining, metallurgical, energy and infrastructure industries.
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