Estimation of methodology and validation of particulate entrainment in a pilot-scale rotary kiln-based hazardous waste incinerator



Combustion gas particulate entrainment from rotary kiln hazardous waste incinerators (HWI) is a necessary design data requirement because of its impact on the design and operation of the downstream process equipment. The particulate leaving the rotary kiln off-gases may slag in the secondary combustion chamber (SCC). The potential to slag and the problems slagging can cause are dependent upon the SCC burner design, the mineralogical composition of the praticulate, and the SCC operating temperature.

Some entrained particulate may adhere to the walls or fall out in the SCC as a dust/stag; the remainder of the particulates will be conveyed by the flue gas to the downstream air pollution control (APC) system. If a wet APC system is used, the particulates would be discharged to a wastewater treatment system (WTS) or publicly operated treatment works (POTW).

A literature search was conducted to determine the knowledge base for particulate carry-over from a countercurrent rotary kiln processing sedimentary solids. No data existed for this type soil. A pilot test was, therefore, conducted to experimentally measure the potential entrainment rate of this material. A detailed discussion of the entrainment mechanisms, pilot test equipment, sampling procedure, test conditions simulating the commercial operation, particle size distribution (PSD) of the ash sample, percent carry-over rate, and measured PSD of the kiln particulate carry-over are presented in this article. A mathematical model was developed by the authors to predict the pilot test results. The PSD of incinerator ash was used to calculate percent carry-over rate and PSD of the entrained solids. A comparison of experimental versus estimated results for estimating entrainment are presented in this article.