Impulse Anywhere is what you're looking for I think.
Yep. Only thing is that you have to download the whole game -- all 2+ GB of it -- every time it's updated.
Seriously, folks, just use Impulse for incremental updates. It's not going to steal your soul or anything.
While that's true, the OP's problem is just that he doesn't have internet at home and has to use a library computer.
In that case, Impulse Anywhere is currently the only option available as folks have mentioned. It's a web-based download that doesn't need the Impulse client. These archives can be installed completely offline. In the future, once they stop putting out 2-3 updates/month, they will DVDs with the latest up to date version that you will be able to get mailed to you. For now, you're going to have to use Anywhere.
The reasoning is nothing particularly sinister, just that Impulse updates by a direct file comparison between your local installation and the version on the distribution network, and then directly replaces any file that needs updating. The benefit is that they don't need to continuously test standalone installers and can increase the frequency of updates. The downside is.. no standalone installers are possible