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 was completed. Task 2. Model Development. During this quarter, the model which now treats semi-infinite solids has been extended to treat small particles with a finite number of layers. Task 3. Measure Alkali Vaporization Rates. in the last quarter, experiments were performed which demonstrate the feasibility of using LIF to measure alkali vaporization rates. As a result of these studies the LIF spectra were obtained for sodium vaporized from the surface of sodium silicate. During this quarter, these experiments have been continued, and the temperature dependence of the vaporization rate has been determined. 5 references, 9 figures.