Solvent Recovery for the Oil Agglomeration Coal-Cleaning Process

摘要

Solvent removal and recovery from coal pellets produced by the spherical agglomeration process were studied. Different types of pellets were prepared using an eastern and a western coal and three grades of solvents. Three dryers, namely Turbo, Roto-louvre, and Holo-flite, were selected for laboratory testing to remove the solvent from the pellets. Results showed that all three dryers can evaporate the solvent from the coal pellets to very low levels;however, a large amount of coal fines was generated in the Holo-flite dryer. Superheated steam and simulated flue gas were tested as the drying media to study the drying and recovery of the solvent from the coal pellets. Solvent recovery was found to be very high when superheated steam was used but very poor when simulated flue gas was used. It is recommended that the Turbo dryer, which has been using superheated steam in some of its commercial units, be studied further on a pilot scale. A flow scheme of the pilot plant is proposed. A preliminary-level economic evaluation is made using Tennessee Valley Authority (TVA) design premises with each of TVA and the Electric Power Research Institute (EPRI) economic premises to compare seven flue gas treatment (FGT) processes for removal of nitrogen oxides (N0X) from power plant flue gas. The case examined is a new, 500-MW unit burning 3.5% sulfur coal and emitting 600 ppm N0X in the flue gas. A minimum removal efficiency of 90% for sulfur oxides (S0X) and N0X and 99.5% for particulates is assumed. To permit comparisons of the dry NOx FGT systems with the wet SOx-NOx systems, which also remove particulates, the costs of both a limestone slurry flue gas desulfurization (FGD) unit and an electrostatic precipitator (ESP) are added to the cost of the dry NOx-only processes and the cost of an ESP is added to the cost of the dry S0x-N0x process.