Lesser noxious emissions with SCR technology [Oct 2011]

November 11, 2011 6:14 am

As NOx emissions are produced by all combustion processes, Dürr EES offers the selective catalytic reduction (SCR) technology for more than just its own air pollution control systems
Environmental technologies are the basis for ecological and economic pollution control in many different industrial sectors. As environmental protection is getting more and more important the emission values will be tightened. Dürr Environmental and Energy Systems (EES) has responded to this: the specialist for environmental equipment now offers selective catalytic systems for the reduction of NOx.
For Dürr EES these new emission limits are relevant mainly for the design of Ecopure VAR thermal oxidizers. Especially for high combustion temperatures of over 1,100° C in the combustion chamber (thermal NOx), and if nitrogen is contained in the fuel (fuel NOx), selective catalytic reduction (SCR) is the only efficient method. In both cases NOx concentrations are high after the combustion process, and these can be reduced with SCR.
In the SCR systems used by Dürr, a reducing agent is first of all injected into the flue gas at temperatures of 260 to 390° C. Suitable substances are, depending on customer’s requirements, gaseous ammonia, ammonia water or urea. The subsequent process is the selective conversion of NOx and NH3 and/or NH2 (as the case may be) to N2 and H2O. Selective means that the nitrous oxides are reduced with first preference, whereas unintentional side reactions of other substances are largely suppressed. In case the flue gas does not have the temperature necessary for catalyst operation, it is heated up to the required temperature. A recuperator (heat exchanger) and burner are installed upstream for this purpose. The heat contained in the purified flue gas is utilized and fed back to the unpurified flue gas via the recuperator.
As NOx emissions are produced by all combustion processes, Dürr EES offers the SCR technology for more than just its own air pollution control systems. Other combustion processes used in steam and power generation systems or in chemical production processes can also be equipped with Dürr’s SCR technology, which is installed as a stand-alone flue gas purification stage. Customers have the option of buying this equipment with or without controls. Especially for gas turbines with a capacity of approx. 30 MW Dürr offers a special system which also operates efficiently at temperatures of 500 to 520° C.
About DürrDürr is a mechanical and plant engineering group that holds leading positions in the world market in its areas of operation. It generates a good 80 per cent of its sales in business with the automotive industry. It furthermore supplies the aircraft, machinery, chemical, and pharmaceutical industries with innovative production and environmental technologies. The Dürr Group operates in the market with three divisions. The paint and assembly systems division supplies production and painting technology, especially for car bodies. Machinery and systems from the Measuring and Process Systems division are used in engine and transmission manufacturing and in final vehicle assembly, among other areas. The third division, Clean Technology Systems, is focused on processes to improve energy efficiency and on exhaust air purification. Dürr has 48 business locations in 21 countries worldwide.
Dürr has been active in India for nearly 50 years, with a local presence for over 20 years. Nearly all of Dürr’s business units with their complete innovative product portfolio are active in India, offering high quality balancing and diagnostic machines, application technology, paint and final assembly systems, as well as environmental systems. Dürr’s wide array of activities in India also includes industrial cleaning and automation solutions and consulting. Dürr has made India an important hub for their worldwide engineering activities offering its customers international know-how and local experience.