Hello Sanjay,
Why do you wish to do that? How are you going to trigger a workflow without an event?
Every workflow needs an event to be triggered. That is the first thing you need to bind with your workflow header, when you create one. The event can either a custom event or a standard event.
There are standard business objects, which have standard events embedded in them. You can bind these events with your workflow. Also custom events can be created by using WAPI FMs.
Regards,
Dnyanesh.