My team is developing an IOS app which is to be used by specified users who are the customer of our hardware product(sensors being used in manufacturing).
Can I release this app through normal Apple APP approval procedure and adopted by app store? Or Apple disallow this kind of app targeting specified customer group to be put in public app store? If can not put into public store, what is the method to release the app to my customers?
You are allowed to put it on the App Store as long as it doesn't use private Apple API. If you prefer it not to be on the App Store, you can enroll for Apple's iOS Enterprise Developer program which allows ad-hoc distribution (at a costly price $$$).
Its generally recommended that if the app is for a specific target group and that outside of the group, the app's useless, its better to release as an internal app instead of on the public app store.