As per my understanding, you can use app server which has both your servlet container and EJB container for deploying your servlets and your business logic, but a much more cleaner architecture is to use a separate servlet container provided by a web server.
So you deploy your servlets on that web server and your beans on an app server. This results in better security as well since your web server will be in the DMZ and the app server behind the second firewall. All the requests coming from the internet will hit only the web server.The app server will only accept requests from the web server or the farm of web servers. Also to support multiple clients, the achitecture looks much better.
The web server can serve the static/dynamic content, This results in better paritioning of the logic as well, so the calls for static content will not reach the app server at all.