| The chemical characterization of phosphate rock of the Phosphoria Formation was determined using C, H, N, O, and S analyses. The physical characterization was determined using particle size distribution and residence time distribution analyses. The overall devolatilization and process pyrolysis behavior of the ore was determined using a thermogravimetric analyzer. The water, carbonate, and elemental analysis compositions were determined for the calcined ore following pyrolysis in a laboratory-scale rotary kiln. The water of constitution decreased by 84.1%, carbon dioxide by 55.4%, and carbon by 41.7% during pyrolysis in the rotary kiln with a 28-minute residence time at a temperature of 1,000°C.; Experiments were performed using air-dried feed material from the Phosphoria Formation of Southeastern Idaho, USA. The process kinetic parameters for the overall phosphate rock decomposition from ambient up to 1,000°C were determined from thermogravimetric data. The elemental analyses, water loss (including evaporation and water of constitution losses), and carbonate decomposition kinetic parameters were determined from rotary kiln data at 200, 400, 600, 800, and 1,000°C. Carbonate decomposition was zero order with an activation energy of 7.107 kcal/mol and a specific reaction rate constant or pre-exponential factor of 0.241 mol/(L·s). The devolatilization of water was first order with an activation energy of 1.277 kcal/mol and a pre-exponential factor of 0.004 s-1. The elemental volatilization data were insufficient to determine the reaction order of N and S; however, it was first order for C, H, and O with activation energies of 10.994, 15.907, and 5.734 kcal/mol for C, H, and O, respectively. The pre-exponential factors were determined to be 7.479 x 1012, 4.052 x 1014, and 2.598 x 1011 s-1 for C, H, N, O, and S, respectively. The overall devolatilization of the ore was first order for the 200, 400, 800, and 1,000°C experiments, but zero order for the 600°C run. Kinetic parameters varied during process experiments according to the different heating rates experienced in the rotary kiln. The activation energies for the 200°C experiment ranged from 4.168 to 6.825 kcal/mol; the pre-exponential factors varied from 1.104 to 27.10 s-1. The activation energies varied from 3.019 to 53.78 kcal/mol and pre-exponential factors from 1.056 x 10-2 to 5.349 x 10 15 s-1 for the 400°C experiment. Activation energies from 1.358 to 91.68 kcal/mol and pre-exponential factors of 2.913 x 10-26 to 17.11 mol/(L·s) were determined for the 600°C run. The 800°C experiment gave activation energies from 5.706 to 26.304 kcal/mol and pre-exponential factors from 8.977 x 10 -6 to 1.315 x 103 s-1. The activation energies for the 1,000°C run ranged from 6.157 to 26.185 kcal/mol; the pre-exponential factors from 1.282 x 10-5 to 1.402 x 103 s-1. |
