Yes you can apply with your jee mains rank through b category.To get the information how to apply ,you can contact the CBES management office located in Himayatnagar or you should regularly check out for notifications in CBIT website(CHAITANYA BHARATHI INSTITUTE OF TECHNOLOGY) .Now I am providing you some probbable cut off rank according to previous year's closing rank :

CSE ---25000

MECH ----40000

IT----60000

ALL THE BEST!!! 

After the main counseling of eamcet about a week later there will be newspaper notification regarding the b category seats and the date of application.

And also do keep visiting the below given link you will get all the details here and you can apply for it through this link

http://www.cbit.ac.in/