You can first get the details of all the sessions in a system and then delete a particular session.
curl -k -X GET 'https://<QS_HOSTNAME>:1443/systems/<systemName>/sessions' --header 'Authorization: Basic <DB_TOKEN>' curl -k -X DELETE 'https://<QS_HOSTNAME>:1443/systems/<systemName>/sessions/<sessionId>' \ --header 'Authorization: Basic <DB_TOKEN>'