Investigation of the Mechanism of Fly-Ash Formation in Coal-Fired Utility Boilers. Quarterly Report, February 1-April 30, 1979

摘要

The current status and objectives of this project are summarized. In the laboratory studies, objective A-4 has been essentially completed with the draft of the technical paper Aggregation and Growth of Submicron Oxide Particles in Flames. We are currently reviewing current literature on coagulation before rewriting the paper and submitting it for publication. The draft copy is attached to this report as Appendix A. Objective A-6, 7, the study of oxides other than silica and oxide mixtures, has just begun. Titania is the oxide under investigation. In the power plant studies, a probe, intended for use in Merrimack No. 1 and No. 2 boilers, has been designed and constructed. The probe is not water cooled, but rather depends on a refractory sheath and dilution air to keep temperatures low enough for survival of the nickel tube. Dilution air mixes with the sample at the probe tip, conveying it to the sample train. Its presence should minimize deposition of particles inside the probe. The fact that the probe is not artificially cooled should also minimize thermophoretic deposition. Original samples will be characterized by impaction and liquid fractionation of filter samples. Another aspect of plant studies is the use of nuclepore filters to fractionate samples of product ash that have been dispersed in a liquid. This is part of an effort to separate and characterize fly ash according to size and composition. The difference between this work and studies done elsewhere is the attention devoted to the submicron condensation-ash particles. Development of a model for sub-micron fly-ash formation continues. A manuscript describing this work has also been prepared and will be found in Appendix B. Separate abstracts were prepared for the two appendixes. (ERA citation 05:020576)