This fluidization studies program was designed to obtain an understanding of the attrition and entrainment of coal chars and limestone/coal-char-mixtures in high-temperature, high-pressure fluidized beds. The tasks in the program were designed to determine: 1. The importance of mechanical, thermal, and chemical-reaction type attrition of coal chars in a fluidized bed. 2. The variation of the entrainment rate of coal char particles as a function of gas density, gas viscosity, and gas velocity. 3. The determination of the effect of limestone addition to the bed on the attrition rate of coal chars in a fluidized bed. 4. The determination of the effect of limestone addition on the entrainment rate of coal char particles as a function of gas density, gas viscosity, and gas velocity. Batch attrition tests at ambient pressure were conducted in a 6-inch-diameter fluidization column using -20 35 mesh sizes of both coke breeze and lignite char. Tests were also conducted with limestone/coal char mixtures to determine what effect the presence of limestone had on the fines generation rate of coal chars in fluidized beds. Limestone concentrations of 20, 35, and 50 weight percent were tested. 10 refs., 62 figs., 19 tabs.