Yes it is possible. But if your IT staff is even mildly competent they will find out and probably not be too pleased. I would suggest living with the limitation. If however you choose not to heed my advice, research bounce (IRC proxy) servers. You will want to find one on port 80, there are hundreds of them so it should not be overly difficult to find one. That should work, though depending on how the firewall is configured it might not.
Alternatvely you could do some port forwarding tricks with SSH. This would require a better knowledge of networking though, as well as an external SSH server (easiest if the ssh server is the IRC server but it is not strictly necessary) and the firewall not blocking port 22. They probably do not.
If nothing else you will learn more about port assignments, forwarding, and proxies then you ever thought you would need. Let me stress though, these kind of tricks piss the IT security people off, trust me.