As Clive said, this replacement can't be done automatically!

there are cases when you really need the double quotes.
on DB2, if the column names where created originally with double quotes like "DeptName", this becomes case sensitive and you are forced to reference them using the double quoties and the proper case names, otherwise you will receive invalid column name error.

And unfortunately, DF convertion from embeeded dat tables to DB2 always create the fields with double quotes. No option to choose during the conversion time.
By the way, this is in my wish list for a long time. I hope some day it get implemented!