A major objective of the US Department of Energy is to increase coal utilization through the development of combustion stream cleanup technologies. Many of the existing cleanup devices as well as advanced concepts rely on heterogeneous processes (i.e. gas-solid interactions) to achieve efficient stream removal. Examples of such devices include particle injection and granular bed filters for alkali removal, limestone injection for SO/sub x/ removal in fluid bed combustors, dry injection for SO/sub x/ removal in entrained combustion, and trace metal adsorption and removal on fly ash. Recent studies indicate that the successful use of turbines in combined cycle processes may depend on understanding the interaction between the gas phase alkali and particles in the combustion stream to substantially reduce turbine corrosion. This report documents progress in efforts to model the heterogeneous chemistry of coal combustion streams as well as laboratory studies to obtain critical input data for the model. Task 1. Exercise PACKAGE Code. During this reporting period, the PACKAGE Code solution model has been used to investigate the combined effects of sulfur dioxide and chlorine on alkali gettering using kaolinite. Task 2. Model Development. Work on this task has focused on implementing the combined segregation, evaporation, and adsorption code. In this report the evaporation terms in the code are characterized and the interaction between segregation and evaporation processes is described. Task 3. Measure Alkali Vaporization Rates. During this quarter, experiments were performed which demonstrate the feasibility of using LIF to measure alkali vaporization rates. As a result of these studies the LIF spectrum has been obtained for sodium vaporized from the surface of sodium silicate to our knowledge, these are the first such spectra to be obtained in this manner. 3 references, 11 figures.