7. Erosion/corrosion of submerged surfaces in fluidized beds

The "fluidity" of the volume occupied by the granular medium, in the fluidization regime, makes it possible to introduce exchange surfaces or tubes. The high external bed-wall coefficients obtained in heat transfer between an immersed tubular exchanger and a fluidized bed of divided solids are one of the main advantages of this type of exchange configuration. However, collisions between the particles in the bed and the exchange tubes, caused by the movement of the solids, can lead to accelerated tube erosion processes, jeopardizing the service life of the plant. Indeed, it must be possible to guarantee a service life of around 100,000 hours. However, the erosion rates experienced by a bundle of metal tubes immersed in the bed of a bubbling fluidized-bed furnace, for example, can reach high values of around 1 to 2.5 mm/1,000 h , leading to operating times of the order of...