#mtgjudge congratulates you on an interesting question
Accumulated Knowledge has two actions:
1) Draw a card
2) Draw cards equal to the number of cards named Accumulated Knowledge in all graveyards
Once you get to part 2, the number of cards you draw gets "locked in". In reality, this is replaced by X instances of "Draw a card" and each one can be replaced by some other effect. If you dredge off one of these draws and dredge into more Accumulated Knowledges, you do not get to draw a card.
If you replace the first draw with Dredge and dredge into more copies of Accumulated Knowledge, the spell will see those extra copies in step 2. So in order to answer your question, yes, if you replace the first draw and hit another AK, you draw 2 more cards, for a total of 3.
To illustrate all of this, imagine you are holding Accumulated Knowledge. No extra copies are in any graveyards. The top two cards of your library are both Accumulated Knowledge. You cast your AK and dredge Grave-Shell Scarab (dredge 1), putting Accumulated Knowledge into your graveyard. The game moves onto the second portion, and translates it into "Draw a card". You replace this draw with Dredge and put the second Accumulated Knowledge into the graveyard. You do not draw any extra cards; you just get the 2 draws.
