GEM has developed and installed numerous systems for "selective non-catalytic reduction" (SNCR) of nitrogen oxides (NOx) in incineration and cremation processes, mounted on skids and applicable to several plants in series.

The reduction of NOx is given by the injection into the secondary chamber of a reagent diluted in aqueous solution, i.e. this method uses a 30% urea solution to reduce NOx in N2 and H2O, reaching an abatement efficiency of approximately 50-60%.

To do this, the system designed by GEM provides for a continuous analysis of NOx in the chimney to dose the quantities of urea as a function of the measured NOx value in real time. Thus the injection is performed only if necessary and managed automatically based on the data received from the continuous analyzer.

The system operates in an optimal temperature range (850-1050 ° C) within which the expected abatement reactions are obtained. In addition to the operating temperature, the system called GEM SIU 144 also takes into account two other parameters to guarantee the efficiency of the system, namely the residence time at the correct temperature (> 0.5 sec) and the high turbulence of the flow of the urea solution (to ensure intimate contact between the urea particles and the flow of fumes).