A. Twist cleaners
D. Zephyr cleaners
I had been asked this question in homework.
Enquiry is from Mechanical Dust Collectors topic in section Steam Power Plant of Energy Engineering
The explanation: Cyclone separators are a part of a group of air pollution control devices known as pre-cleaners as they generally used to roughly remove large pieces of particulate matter. This prevents finer filtration methods from having to deal with large, more abrasive particles later on.