The fluidized bed heat transfer characteristics of vertical finned and unfinned tube heat exchangers were examined in a 12-inch FluoSolids Reactor. Four different heat exchanger tubes were used. The studies were conducted on an isolated U-tube immersed in a fluidized bed combustor burning a high sulfur coal with either dolomite or limestone used as the sulfur sorbent. The unit was operated at atmospheric pressure, 1650/sup 0/F bed temperature and superficial velocities up to 3.25 fps. The following results were obtained: (1) Very high bed-to-tube heat transfer coefficients, in the range of 118 - 137 Btu/hr ft/sup 2/ /sup 0/F were obtained with a bare tube using air as a cooling medium. (2) The coefficients with the finned tubes were in the range of 48 - 91 Btu/hr ft/sup 2/ /sup 0/F. The higher coefficients were obtained on tubes having fewer fins. The highest overall external heat transfer however, was provided by the finned tube having the largest number of fins. (3) The heat transfer coefficients were greatly affected by the mean particle size of the bed material. The coefficient increased as the bed average size decreased. (4) The heat transfer coefficient increased as the fin height decreased, but it did not increase as fast as the heat transfer area decreased. (5) High combustion efficiencies in the 99.6 to 99.8% range were observed and were attributed to the use of a cyclone recycle system and a deep bed. (6) The freeboard dust loading was approximately 350 to 550 grains/ACF with dolomite feed and a cyclone recycle system.
Engineer, design, construct, test and evaluate a pressurized fluidized bed pilot plant using high sulfur coal for production of electric power