Wanchain has burned the 21 million WAN (10% of total, reserved for PoS rewards) by sending them to an address where the WAN is not recoverable.
Here is the address: https://wanscan.org/address/0x0000000000000000000000000000000000000000
The tx: https://wanscan.org/tx/0x6bc3b697e48b95793aae27b8e9aa84f98eebe5beb024b4a051b5845ef547d865
PoS rewards are explained here:
https://medium.com/wanchain-foundation/wanchain-proof-of-stake-validator-economics-for-upcoming-alpha-testing-d57353a4d0f9
As far as I understand they didn't burn them in fact as this tokens were went out from total supply, not from circulating supply ad will be adding as rewards per POS mining... ?