In order to collect information for incentives while keeping a survey anonymous, you can create 2 surveys in Qualtrics and keep them separate. The one with the data will be an anonymous survey.  At the end, you would post a link to a second, separate survey that asks for email address or name to collect information for incentives.  

Also, make sure that you not only test the survey by having your lab take the survey, but then to go to where the data is stored to make sure the process generates two different databases - one for data you want to analyze and another for contact data for incentives. Then, delete that preview data before distributing for the actual study.  If the databases are not separate, then your survey will not be anonymous!

Make sure to anonymize responses as shown here.