Conflict identification and resolution is a key phase of requirements engineering. It is crucial to identify conflicts at early stages of the requirements engineering which in turns helps in establishing a cohesive set of requirements to guide the overall requirements engineering process. Conflicts especially arise due to the self reinforcing or contradictory nature of some NFRs (e.g. efficiency and usability). This paper describes how quality ontologies can be used to support the identification of NFR conflicts and facilitate discussion towards requirements prioritization tasks in requirements engineering. Our approach is based on using the ISO/IEC 9126 quality ontology to underpin the NFR description and reasoning mechanisms to pinpoint potential NFR conflicts that need to be further discussed by stakeholders. The work is implemented in the ElicitO requirements elicitation tool. We also report results of applying the approach and the tool to identify conflicts in requirements elicitation activities at the student intranet project of the University of Manchester (Manchester Unity Web Project).