The subject says it all... ;-)

It seems to be not possible: https://powerusers.microsoft.com/t5/Flow-Forum/Flow-Admin-Center-how-to-delete-an-environment/m-p/10067

How do you delete an environment in Microsoft Flow?

Dean_Gross
Silver Contributor
Dec 15, 2016
I wonder who in MS made the decision that this product was ready for GA when it did not include this basic level of functionality. The deployment processes since May 4 have been heavily focused on speed instead of quality.
jcgonzalezmartin
MVP
Dec 14, 2016
It seems to be not possible: https://powerusers.microsoft.com/t5/Flow-Forum/Flow-Admin-Center-how-to-delete-an-environment/m-p/10067
Dean_Gross
Silver Contributor
Apr 05, 2017
It is now possible to Delete an environment, go to the Details page, there is a small Delete this environment link at the bottom. FYI, you must remove all Flows before you remove an environment
- Salvatore Biscari
  Silver Contributor
  Apr 05, 2017
  Thank you, Dean!
- Gilles Pion
  Copper Contributor
  Jun 10, 2017
  Dean_Gross wrote:
  It is now possible to Delete an environment, go to the Details page,
  From https://flow.microsoft.com I don't see any "detail" page
  - Dean_Gross
    Silver Contributor
    Jun 10, 2017
    Click the Gear, choose Admin Center, then you can navigate the Environments