It might work, but as HareBrain says it rather depends on the strength of your prose and exactly how you tell it.
I have an info dump giving important back story, which is told from omniscient narrator -- and it is all exposition, no characters or dialogue at all. I think it works (and someone whose opinion I respect agrees), but it's half-way through the book, after 46,500 words, so anyone who's got that far would be interested in knowing what happened, and it's only 1,400 words in itself. I then seque straight from that info dump into a scene for which the information is important, with a good-ish linking line between the two.
What I suggest you do is write it in the most concentrated form you can, as if you were making notes for someone, and see how low you can bring the word count. If you have used omniscient narrator at all in the previous 20k words, try the info-dump as exposition only and see if it works. If you don't like the tone of voice used, try working it as exposition but from one character's POV -- diary entries, history project, a letter of explanation. If it still jars too much, or these devices have no place in the story, then you'll have to bring it out in dialogue, and probably best fed into the book in dribs and drabs. (Of course, diary entries and letter extracts etc could be dribbled in as well over several chapters.) In which case, make sure your narrating character is telling someone who doesn't know and couldn't know the back story.