Spiritual and ritual are two different words that have different meanings. The two words can be used in both noun and adjective form in a sentence though, but they are not related in meaning. Foremost, spiritual is considered a term that is pertaining to the spirit or soul; an abstract and unexplainable part of the human that goes a bit farther beyond the normal human physical understanding.
Spiritual is also term that is used in pertaining to God or a sacred place (of worship). Spiritual is pertaining to a realm that cannot be contacted just by the human psychology or physical medium. Should I say? It takes the spiritual to contact the spiritual.
Ritual, on the other hand, is simply pertaining to a kind of rite that is being carried out consistently. As a matter of fact, there is a very close relationship between ritual and rite; probably that would make you have more understanding of it. Ritual is simply related to a custom, which can actually be spiritual.