I had a similar thought when I first read the Lawrence Livermore article. This didn't however appear to be the outcome of their lab scale demonstration. The Arrhenius definition of an acid is a substance that, when added to water, increases the concentration of H+ ions. It seems to me that almost by definition the removal of H+ ions from water produces a base. Also ocean acidity appears to be a matter of where it occurs. The Climateprogress piece Ocean Acidification, Wildfires Are Taking Their Toll On The Pacific Northwest points out that acidification only became a problem when CO2 levels of 900 to 1,000 parts per million - almost triple normal levels - were upwelled into theeuphotic zone. With OTEC and a deep water condenser you could vent most of the chlorine at a depths of about 1000 meters. These waters would be very slow to mix back to the surface. You would still convert the CO2 but negate the acidity problem. Another alternative is you can produce other products with some of the chlorine. Some of its uses are outline here but it is probably not something you want to see at the surface.