Labelling of particulate matter for tracer studies in incinerators, sedimentation tanks and mixers

Abstract The investigation of the transport of particulate matter in industrial processes is often advantageously performed using radioactive tracers. Non-isotope labelling is often necessary because of lack of conveniently activable isotopes in the material under investigation. 56 Mn, 140 La, 198 Au and 51 Cr are radioisotopes commonly used for labelling such materials. The labelling techniques involve either a simple soaking of the particles with a solution of the tracer or a surface labelling procedure. 198 Au has proved to be a most applicable tracer because of the easy access in a colloidal suspension as radiopharmaceutical. The suspension is simply absorbed on many materials. Three experiments are described, a retention time distribution study in kilns in a refuse incinerator using 140 La, a mixing study of concrete mixers using 198 Au and a retention time distribution study in a sedimentation tank for activated sludge in sewage treatment plants.