Разделите данные на основе количества строк
DataTable[] splittedtables = tbl.AsEnumerable()
.Select((row, index) => new { row, index })
.GroupBy(x => x.index / 12) // integer division, the fractional part is truncated
.Select(g => g.Select(x => x.row).CopyToDataTable())
.ToArray();
Xenophobic Xenomorph