Potassium Seed Activities in Open-Cycle MHD System: Predictions Using a Multiphase Multicomponent Solution Model

摘要

Although the importance of seed recovery in the open cycle coal fired MHD System has been established, complete understanding of the complex chemistry existing at high temperature between potassium seed and coal-ash constituents is still lacking. A multiphase, multicomponent solution model was developed by modifying the widely used NASA computer program for calculation of complex chemical equilibrium compositions to include a subroutine that calculates solution formation from the condensed phase species. This model has been used to predict the potassium activity in the K sub 2 O + SiO sub 2 , K sub 2 O + SiO sub 2 Al sub 2 O sub 3 , K sub 2 O + SiO sub 2 + MgO, and K sub 2 O + SiO sub 2 + CaO systems over the temperature range of 2300 to 1200 K, in which condensed phase components (i.e., K sub 2 SiO sub 3 , K sub 2 Si sub 2 O sub 5 ...) were assumed to form an ideal solution. Calculations showed that the addition of Al sub 2 O sub 3 , CaO, or MgO to the K sub 2 O + SiO sub 2 binary system resulted in an increase in potassium activity in the gas phase, especially for CaO. Such information improves our predictive capability and may be used in the selection of materials and in establishing optimum conditions for operation of the combustor-generator high-temperature air heater components of an open cycle MHD system. Further, the predictive capability of the program can be used to assess other, more suitable additives and in determining operating conditions for improved potassium seed recovery. (ERA citation 04:033898)