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NDIR gas analysers from Sick

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The NDIR gas analysers (S721 Ex) by Sick can measure the sum of CO and CO2 with only one IR module – certified for Ex-Zone 1.

Many processes of the chemical industry require high-purity hydrogen, e.g. for the catalytic hydrogenation. For the generation of hydrogen different techniques are used. Often natural gas or higher hydrocarbons are converted to synthetic gas, a mixture of hydrogen and carbon monoxide, by adding steam in so-called reformers. A major part of the carbon monoxide (CO) is then oxidized to carbon dioxide (CO2). Afterwards the hydrogen is purified in a pressure swing adsorption process to a percentage of 99.999 Vol%.

The purity of H2 is continuously monitored at the absorber column outlets. The measuring points are located in the hazardous area which calls for a severe safety standard. Consequently the requirements for the application solution and the measuring device are very high. Moreover the measuring devices are expected to be economic and easy to handle. The immediate on-site service is a precondition.

Thanks to their special design the NDIR gas analysers S721 Ex can measure the sum of CO and CO2 with only one IR module UNOR. With the special filling of the detector and a special optical filter both components can be detected from 0 to 50 ppm at the same time. The gas analyser module UNOR is placed in a flame-proof housing type S721 Ex (ATEX-category II 2 G). The display has also a flame-proof enclosure, the keyboard is intrinsically safe. This model is certified according to ATEX for the application in Ex-Zone 1.

Hydrogen gas can’t escape as the gas paths are tubed with stainless steel. A pressure reducer in the system provides an easy gas sampling and the sample conditioning with redundant filters simplifies the measurement. The filters can be exchanged under operation, idle time is avoided. An integrated pressure control valve prevents a dangerous pressure increase in the system which may lead to a leakage of hydrogen containing sample gas.

Linde has delivered hydrogen for a number of applications since 1910, for example in the chemical, petrochemical and food industry. In an important project for one of the largest refineries of India the gas analysers S721 Ex are integrated to monitor the purity. Determining factors were SICK’s experience in systems building, the start-up by an own local subsidiary and the immediate help on site in case of technical questions and problems including maintenance.

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