how to vent an electric dryer when outdoors isn't option
The proper answer for this, and certainly the one the building was built for, is to use a condensing dryer. This is a special dryer with a dehumidifier built in, which then overboards the recovered moisture into the drain  intended for the washer.  

I suppose you could do the same thing with an actual dehumdifier.  If you can find a way to install it above the washer drain, almost any model will let you  route a hose from its output,  so the bucket never fills up.   Some dehumidifiers also have a water pump to push the drain water uphill if needed.