SOOT SENSOR-BASED ON A POROUS SOLID-ELECTROLYTE CELL

Diesel engines or oil burners emit gaseous reaction products (CO2, CO, H-2, SO(x), NO(x), H2O) as well as solids (soot, oil-coke). Soot dete ction in flue gases is important for the optimization of combustion pr ocesses and the surveillance of legislative emission limits. In contra st to the measurement of gaseous emissions the measurement of soot con centrations is not so well developed. Most of the commonly used method s can only determine the optical extinction (soot numbers) of the flue gas and not the ecological significant concentration of soot particle s. A new electrochemical method for in situ measurement of soot concen tration in flue gases is presented. A potentiometric soot sensor based on a porous oxygen-ion-conducting ZrO2 solid electrolyte cell heated to more than 500-degrees-C was developed. By pumping soot-loaded flue gas through the porous solid electrolyte the soot particles are filter ed and collected at the hot working electrode. The combustion of soot at the hot working electrode changes the oxygen chemical potential at the sites where soot particles are attached and generates an e.m.f. Th e sensor shows reproducible voltage when exposed to the same soot conc entration.