There are a number of ways to do this: this is one I've used
successfully.

1. Insert a new column on the extreme left of the data, and data-fill
it consecutively from 1 to 46000.
2. Sort your data on any appropriate column. All the blank rows will
appear either before or after the sorted data. Delete those rows (they
have numbers from step 1 in column A).
3. Sort again on the numbers you entered in column A to put your data
back into it's original order.

Vwalla!