DIRECT-CONTACT STEAM CONDENSATION WITH SIMULTANEOUS NONCONDENSABLE GAS-ABSORPTION

Experimental results are reported on simultaneous heat transfer and ga s dissolution during the direct-contact condensation of steam on water in the presence of CO2. A column filled with structured packing is us ed as condenser with the water in counterflow with the steam/CO2 mixtu re. The region along the column where the bulk of condensation takes p lace is controllable by suitable choice of the steam/wafer ratio. Meas ured local heat-transfer coefficients change by roughly an order of ma gnitude from the bottom to the top of the column. The extent of CO2 di ssolution in the water/condensate under most conditions is unexpectedl y high and depends strongly on the exit liquid temperature. A driving force based on the interfacial CO2 concentration, not the overall conc entration difference used in conventional absorption operations, is su ggested as more appropriate to describe the phenomenon. The data are c omplemented with preliminary results from a computational model based on the integration along the column of local heat- and mass-transfer r ates.