De-NOx plants

In recent years the number of Selective Catalytic Reduction (SCR) and Selective Non-Catalytic Reduction (SNCR) plants for De-NOx have increased significantly. Continuous analysis of NOx prior to the de-NOx plant is often required to measure the concentration generated by the combustion process. This may be required to provide feed-forward to the Ammonia/Urea injection system and also to allow the effectiveness of the reduction process to be assessed.

Continuous analysis of NOx post-reduction is required to allow the effectiveness of the reduction process to be assessed. It may also be beneficial to monitor NH3 slippage at this stage by calculating from the pre and post NOx levels if excess Ammonia/Urea is being applied.

Where sulphur-bearing fuels are used, other unfortunate reactions make conventional continuous gas analysis very difficult. Below 300°C, Ammonia and SO3 react to form solids in the form of Ammonium Bisulphate (ABS) and Ammonium Sulphate salts. These clog up the catalysts very quickly and reduce the efficiency of the plant.

To monitor the NO and NO2 (NOx) pre and post the de-NOx system , the CODEL GCEM-40E analyser is extremely effective where a sample is continuously extracted from the duct via a multiple-filtered probe with pre-shield and automatic reverse blow-back system.

It is worth noting that conventional extractive systems require the sampled gas to be cleaned and dried to a very high standard prior to analysis invariably resulting in an extremely high maintenance demand. Such elaborate pre-conditioning is not required by the CODEL GCEM-40E analyser ensuring maximum availability even under these arduous conditions.

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