The information presented constitutes the report for the period July 1 to September 30, 1996. Characterization of intraparticle mass transport limitations during pyrite oxidation was embarked upon. The effort was intended to confirm that intraparticle transport limitations are negligible. Samples of 20 micron pyrite particles extracted from the flow reactor after oxidation at 1550 K in 1% oxygen level were analyzed. The samples has been extracted after reaction times of 42 ms, 52 ms, 77 ms, and 146 ms. For these samples, the bulk product compositions previously determined by X-ray diffraction analysis consisted of varying proportions of FeS2, Fe{sub 1-X}S, FeO, and Fe3O4. The particles were analyzed to determine if the iron compounds previously identified by bulk X- ray diffraction analysis (XRD) were well mixed within individual particles. The extracted pyrite particles, epoxied and sectioned, were subjected to a variety of analytical techniques using the microprobe (JEOL 733 Superprobe). Secondary electron and backscatter electron imaging was performed. Iron, sulfur, and oxygen elemental X-ray maps were generated. Energy dispersive spectrometry was used for qualitative elemental analysis of selected particles. These particles were subsequently subjected to qualitative elemental analysis by wavelength dispersive spectrometry (WDS) using Fe2O3 and FeS2 as standards. During WDS analysis, micron-radius hemispherical volumes bisected by sectioning plane were sampled. The microprobe analyses of oxidized pyrite showed that, generally, particles could be modeled as well-stirred, having negligible compositional gradients of the scale of the particle radius. In all four samples of pyrite analyzed, there were particle edge effects. Furthermore, there were finger-like projections of different phases in mixed-phase particles. Nevertheless, compositional gradients were of concern only in the 77 ms samples.

This document is the eighth quarterly status report on a project that is conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California and is concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO(subscript x) pulverized coal (P.C.) combustion. In general, the project has the following objectives: (1) the characterization of the various mechanisms of intraparticle mass transfer and chemical reaction that control overall pyrite combustion rates and (2) the synthesis of the reaction rate resistances of the various mechanisms into a general rate expression for pyrite combustion. The knowledge gained from this project will be incorporated into numerical codes and utilized to formulate slagging abatement strategies involving the minor adjustment of firing conditions. Ultimately, the benefit of this research program is intended to be an increase in the range of coals compatible with staged, low-NO{sub X} combustor retrofits.

This document is the seventh quarterly status report on a project that is conducted at the High Temperature Gasdynamics Laboratory at Stanford University, Stanford, California and is concerned with enhancing the transformation of iron pyrite to non-slagging species during staged, low-NO{sub X} pulverized coal (P.C.) combustion. The project aims to identify the mechanisms of pyrite combustion and to quantify their effects, in order to formulate a general rate expression for the combustion of pyrite that accounts for coal properties as well as furnace conditions. In general, the project has the following objectives: 1) the characterization of the various mechanisms of intraparticle mass transfer and chemical reaction that control overall pyrite combustion rates and 2) the synthesis of the reaction rate resistances of the various mechanisms into a general rate expression for pyrite combustion. The knowledge gained from this project will be incorporated into numerical codes and utilized to formulate slagging abatement strategies involving the minor adjustment of firing conditions. Ultimately, the benefit of this research program is intended to be an increase in the range of coals compatible with staged, low-NO{sub X} combustor retrofits. 9 refs., 12 figs.

This report describes research on coal combustion processes and pyrite oxidation processes. Work focuses on the oxidation of iron pyrite to form the non-slagging magnetite.

The book highlights and analyses the distress to buildings caused by sulphate-induced heave, with particular reference to the recent problems in the Dublin area of Ireland. It describes the formation of pyrite, the processes involved in its oxidation and the various ways in which consequential expansion takes place. For the first time in the literature it discusses the way that buildings can be raised above their supporting foundation walls by the expansion of pyritiferous fill which has been used beneath ground-bearing floor slabs in Ireland. The significance of fractures through the iron sulphide microcrystals for the rate and extent of oxidation is discussed. Photographs and profiles of sulphate ingress into concrete/concrete blocks are presented. Case histories from the UK, North America and Ireland are discussed.