Your new destination is Falcone Shipping Yard. You have to get there without the Batmobile, as it is currently providing power to the generator near the first antenna. Land on the roof of the small building and turn on detective mode. You will see five thugs and a hostage inside. Move to one of the vantage points nearby and face the exit from the room with the thugs. Open the inventory and choose normal Batarang. Throw it so that it hits the ground near the exit door. When you do it correctly, two thugs should go outside.
Now you have to eliminate both the enemies without raising alarm. You can do it on many ways. The easiest one is to glide towards the thugs, land behind their backs and execute them silently. You can also use other methods, like for example wait for the enemies to stand under the vantage points or use ventilation shafts in the floor to easily get near the opponents.
Batman will soon contact Lucius Fox. Stand in the place marked by the game and wait until Wayne's friend brings you a new version of the Batsuit (8.03). After learning its new functions, head to the room where there are still three enemies left. Use detective mode to locate a ventilation shaft that will take you inside the building.
Note - After wearing the new suit, the game will suggest participating in training sessions (you will see the icons around you). You can do that if you want to, but it is not required to complete the mission.
When you are in the room with three armed thugs, press the attack key/button to activate Fear Multi-Takedown. Batman will automatically attack the first enemy and you just have to jump to the next enemy in slow motion. You should eliminate all the opponents without any trouble.
You can now free Detective Cottell. Next, use the Remote Hacking Device on the terminal nearby.
Now you need to complete a simple puzzle. The goal is to turn both the receivers in the right way (they have to face the Ace Chemicals building located on the right). The solution is shown on the screen above.