I once played some music through a friends Denon receiver and ever since, I now have their receiver listed in my devices to play to.
There's no way for me to remove it. The app on iOS has an option to remove from the list, but it just comes back after a bit.
VERY annoying since I also have a DENON receiver and the model numbers on them are both the same. So I NEVER know which one is actually mine, and frequently play music to their receiver on the other side of town.
I've Googled this issue to no tomorrow, but it appears that there is no resolve for it other than creating a new Spotify account.