You can run multiple nginx sessions by seperating the config between them, the main http section will have to use a 'uniqe' port for each session, from there on you can seperate out the hosted websites and also assign each session its own cpu. You are however limited to a 65.000 connection max for all sessions.

Another, easier, way for multiple sessions is to use 1 session as proxy to many secondairy sessions which will make routing the http port easier, this way also scales better.