In many cases of severe fouling and/or scaling of conventional heat exchangers fluidized bed heat exchangers can be expected to operate continuously with clean tube walls. Especially advantageous are circulating fluidized beds due to their wide range of process stability. But internal particle circulation is inevitably connected to backmixing of the fluid and as a consequence, losses of mean driving force. The losses are negligibly small in case of forced convection evaporators but have to be considered in case of countercurrent Liquid-liquid heat exchangers. Tube erosion by the fluidized particles is surprisingly low as long as the heat exchangers are operated within the range of design conditions. The paper discusses main design criteria and, even more important, costs and long time operational experiences of 15 industrial fluidized bed heat exchangers, some of them logging more than 40,000 hours of operation.