To solve the problem that it is difficult to remove the fouling on the outside wall of heat transfer tubes, the new technology has been developed with double circulation of three-phase fluidization in shell side. A large pesiglass experiment unit is set up, in which heat transfer tubes of 32mm diameter are 2000mm long and the inside diameter of the shell is 500mm. The experiments show that two holes-tube can not only make the three-phase fluidized-bed to circulate in two opposite directions respectively in the cross section but also make it circulate in the longitudinal section. This can guarantee the fouling be removed evenly and quickly through the tubes. The particles move very severely when flowing cross the tubes. It takes only half hour to remove the fouling. The calculation formula of the amount of needed air is obtained. Using this technique, the equipment is of simple structure and low cost. The operation is easy. This technology has been successfully applied in industry for more than 5 years.
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