Abstract: A raining bed heat exchanger includes: a hollow stack; a feed inlet located near the top of the stack for introducing particulate material into the stack so that the material falls through the stack; a gas inlet located near the bottom of the stack for introducing rising gases into the stack so that the gases flow counter to the falling material; a plurality of baffles supported within the stack between the feed and gas inlets for retarding the falling material and prolonging its exposure to the gases; and a disengagement section located near the top of the stack for separating from the gases particulates entrained by the rising gases. The disengagement section includes a screen positioned within the stack and having a plurality of gaps through which the rising gases pass in order to sufficiently separate the entrained particulates. Alternatively, the disengagement section can include a filter media to separate the entrained particulates.