SURVEY OF LONG-TIME BEHAVIOR AND COSTS OF INDUSTRIAL FLUIDIZED-BED HEAT-EXCHANGERS

In many cases of severe fouling and/or scaling of conventional heat ex changers fluidized bed heat exchangers can be expected to operate cont inuously with clean tube walls. Especially advantageous are circulatin g fluidized beds due to their wide range of process stability. But int ernal particle circulation is inevitably connected to backmixing of th e fluid and as a consequence, losses of mean driving force. The losses are negligibly small in case of forced convection evaporators but hav e to be considered in case of countercurrent Liquid-liquid heat exchan gers. Tube erosion by the fluidized particles is surprisingly low as l ong as the heat exchangers are operated within the range of design con ditions. The paper discusses main design criteria and, even more impor tant, costs and long time operational experiences of 15 industrial flu idized bed heat exchangers, some of them logging more than 40,000 hour s of operation.