AIChE Journal, Vol.41, No.2, 241-250, 1995
Direct-Contact Steam Condensation with Simultaneous Noncondensable Gas-Absorption
Experimental results are reported on simultaneous heat transfer and gas dissolution during the direct-contact condensation of steam on water in the presence of CO2. A column filled with structured packing is used as condenser with the water in counterflow with the steam/CO2 mixture. The region along the column where the bulk of condensation takes place is controllable by suitable choice of the steam/wafer ratio. Measured local heat-transfer coefficients change by roughly an order of magnitude from the bottom to the top of the column. The extent of CO2 dissolution in the water/condensate under most conditions is unexpectedly high and depends strongly on the exit liquid temperature. A driving force based on the interfacial CO2 concentration, not the overall concentration difference used in conventional absorption operations, is suggested as more appropriate to describe the phenomenon. The data are complemented with preliminary results from a computational model based on the integration along the column of local heat- and mass-transfer rates.
Keywords:COLUMNS