TY - JOUR
AU - Elsener, Martin
AB - The selective catalytic reduction of nitrogen oxides with ammonia (ammonia SCR) and urea (urea SCR), respectively, is a widespread process to clean flue and diesel exhaust gases due to its simplicity and efficiency. The main challenge of the process is to minimize the ammonia emissions downstream of the SCR catalyst. We found that ammonia emissions of >10 ppm can reliably be detected with a simple pH electrode in the presence of CO2, SOx, NOx, and moderately weak organic acids. 1020 ppm of ammonia in the exhaust gas are sufficient to neutralize the acids and to increase the pH value from 3 to 6. On this basis a continuous measuring method for ammonia was developed, which was used to control the dosage of urea in the SCR process. While keeping the ammonia emissions after the SCR catalyst at 530 ppm an average NOx removal efficiency (DeNOx) of >95% were achieved at a diesel test rig. The method can also be applied for exhaust gases with higher acid contents, if a basic pre-filter is added adsorbing the acidic exhaust components. Compared to water as absorption solution, more precise ammonia measurements are possible, if a 0.1 M NH4Cl absorption solution is applied, whose pH value is changing as a Nernst function of the ammonia concentration.
TI - Ammonia measurement with a pH electrode in the ammonia/urea-SCR process
JF - Measurement Science and Technology
DO - 10.1088/0957-0233/18/3/029
DA - 2007-03-01
UR - https://www.deepdyve.com/lp/iop-publishing/ammonia-measurement-with-a-ph-electrode-in-the-ammonia-urea-scr-SwFG0qH9vR
SP - 771
VL - 18
IS - 3
DP - DeepDyve
ER -