Right, I was thinking you *should* be disposing of the ksession (and maybe this is causing multiple processes to get started). You can keep the KnowledgeBase around, and still dispose the KnowledgeSession:
A knowledge base can be shared across sessions and usually is only created once, at the start of the application (as creating a knowledge base can be rather heavy-weight as it involves parsing and compiling the process definitions). Knowledge bases can be dynamically changed (so you can add or remove processes at runtime).
Sessions can be created based on a knowledge base and are used to execute processes and interact with the engine. You can create as many independent session as you need and creating a session is considered relatively lightweight.