This method is for Blockchain.info's new HD wallet that is made of a BIP39 recovery seed. You must have the backup of the 12-word seeds or phrases from your Blockchain.info's wallet. Which is the only way to gain access to the addresses of your wallet. You must be careful of doing this and recommended that do this offline.
Requirements:
12-word seed/ recovery phrase
Bip39 Converter. Github link: https://github.com/iancoleman/bip39
Brain
Download or clone the repository of the Bip39 converter from the link above.
Once downloaded, open the bip39-standalone.html file
copy your 12 -word recovery phrase and paste it on the "BIP39 Mnemonic's" textbox and wait for "Calculating"
once done, scroll down and you will see a bunch of bitcoin address and its private keys below of "Derive Addresses".
Now you can choose the address that you want to recover and import it in any client that has an import of private key features. e.g. Electrum desktop/mobile wallet, Mycelium wallet and so forth. If you want to import the whole HD wallets as once import only you can copy the private key on the "Account Extended Private " which begins with "xprv", and you can import it on Electrum also and mycelium.
Once done. Then Congrats! :D
Full tutorial with video is on my site: https://bl4nkcode.info
Read more: https://bl4nkcode.info/bitcoin/how_to_export_blockchain_wallet_private_key