Types of cfbc boilers

From a neutral perspective following are the types of cfbc boilers:
a) Cold cyclone CFBC: Called as cold cyclone because cyclone temperature is "colder" (approx 400 Deg C) than a hot cyclone cfbc, which is because of some heating surfaces in the first pass. Aim is to have bed temperature at around 850 Deg C to aid in desulphurisation.

b) Hot cyclone CFBC: Heating surfaces in the second pass, hence cyclone is hotter.

c) Compact cyclone CFBC: Cyclone is part of pressure part circuit, done to reduce bed temperature.

d) U beam CFBC: U beams used instead of cyclone for filtering out coarse ash. Similar in nature as hot cyclone cfbc.