How can I hide from my friends the fact that I do not ever want to be in a romantic relationship...?

you don't have to explain anything to anybody. if they are truly yu friend they would accept you as you are. you say that you will never reveal the reason why but may be if you can get some counseling that will help you to see different about why you don't want a relationship. at 23 you are too young to be alone whatever the reason.