APPLICATION NOTE LD13-02 Measurement of nitrogen in a mixture of Argon/Oxygen (crude argon) online with the LD8000-Crude
The measurement online of nitrogen in UHP argon is widely used and the LD8000 is now a reference in such measurement. However when measuring crude argon with a few % of oxygen, the conventional online instruments are not suitable anymore. Such crude liquid argon (also called CLAR) needs to be analyzed in many cases to be sure the level of nitrogen is within the specification either as a final product for steelmaking or welding applications or before being purified to produce UHP argon . Good analytical tool is then required to have a good process control. The use of Gas Chromatograph (GC) has been widely used to measure this nitrogen level. Even if GC is giving good and accurate results, the analysis time is quite long. In many cases the response time is too long to take proper action if the nitrogen goes too high in concentration. A few minutes are required to get the analysis results and this delay can bring a lot of problems to the plant if it increases suddenly. The need of having an online instrument with a few second response time has been desired for a long time. The LD8000-Crude can now achieve this task and give a better process control for any plant or application that needs to measure N2 in the Crude Argon having up to 5% oxygen. DESIGN: The LD8000-Crude is still using the unique PlasmaDetek technology, but incorporated in a special design, it makes possible to have this plasma emission detector (PED) working with up to 5% oxygen. Common PED cannot create a stable plasma with oxygen. The interference and instability of the plasma is a big challenge. But LDetek has developed a method and a design to have such argon micro-plasma being able to measure from ppb to % of nitrogen with up to 5% oxygen. A specific algorithm has been developed and implemented in the microcontroller unit giving a linear and accurate measurement of nitrogen.
With the 3U cabinet, this instrument can fit in any rackmount cabinet or plant installation. No need of carrier gas and external consumable parts like purifier or oxygen scrubber. Only sample is needed to provide this quick measurement. The micro controller unit inside combined with the LCD display provide a user friendly interface easy to operate. But it also gives all features that such instrument needs on a plant (dry contact relay for range ID, status contact for error monitoring, 4-20 mA output for value reading, auto-resolve alarms system, etc). RESPONSE TIME: The response time for such application is critical. The use of a gas chromatograph has been widely used and it gives good results, however the analysis time can be as high as 5-6 minutes. It is very important, in most of such applications, to have a quick response time to act quickly on the process when the level of nitrogen goes too high. Using the LD8000-Crude, you get a response time of a few seconds (T90 < 20 sec) with a measurement of a few ppm. With the 4-20mA output signal, the process plant can track the level of nitrogen continuously. If serial communication is required, this instrument can send and be controlled by such communication port. HIGHER OXYGEN CONTENT: For measurement of N2 in Crude Argon containing more than 5% Oxygen level, the LD8000-Crude instrument can be configured to achieve such task. The unique plasma detection system (PED) for Crude Argon measurement stays the same. An additional module for sample gas treatment is added to the instrument, which makes the detection of N2 in Crude Argon having more than 5% Oxygen possible. For more information and details, do not hesitate to contact LDetek. 
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Phone: 418 755-1319 • Fax: 418 755-1329 • info@ldetek.com •
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