Abstract: An apparatus for particulate solids (e.g. FCC catalyst) regeneration comprising a regenerator housing containing fluidization means arranged below spent-solids inlet means and regenerated-solids outlet means and having fluid in- and outlet means, and further comprising at least one external heat exchanger housing containing heat exchanger means and communicating with the regenerator housing via solids in- and outlet means in which apparatus at least one solids outlet means directly connect a lower section of the heat exchanger housing(s) with a section of the regeneration housing above the fluidization means.