Is there a way of removing grain from a cgi animation in after effects? (not the video kind.)
As an alternative to the denoising method suggested by @CoinRocket, you could try to export the scene from Blender with less noise. If you have enough computation capacity, this will be a superior solution since post-denoising will always introduce some amount of blurriness into your video. 

The noise in your example image looks like fireflies, i.e. artifacts that stem from the nature of the Cycles Engine in Blender which is based on ray-tracing. There are several ways to reduce fireflies, however depending on your settings and available hardware render times will become extremely long. A while ago, I exported a 15-second sequence at 1000 samples and 24 frames per second rendered for three days straight on my laptop. So be warned.

The easiest way to reduce fireflies is to increase the number of samples the program runs during export. This will correlate directly with rendering times.

There are several other settings that can affect the occurance of fireflies, but some of them are well-hidden. Here's an explanation of some of them. There are also some tricks and workarounds that can help with that, here's an article detailing some of them. You might find some more on the Blender.SE or through other sources. A while ago, I assorted some Tutorials on several techniques in Blender, you can find it here. The titles are in German, but the links in the first tile on the left side might still be helpful to you.