If you're in the market for chemical engineers, it might be best to get paired up with a chemical engineer consultant to aid in your search. Engineering recruiters are only helpful if they are familiar with the job that their candidate search is supposed to fill. Only choose a recruiter that has a solid knowledge base in engineering.
Chemical engineer recruiters will only be successful if they understand the actual work a chemical engineer does on a day-to-day basis. If all your recruiter is doing is searching for keywords and checking if the candidates have an engineering degree, there will be a lot of work left for you to do. Find a recruiter who can eliminate the initial weeding out of unqualified candidates to save yourself time and money.