OCR Text |
Show o Product agglomerate unit operations. The heptane process requires thermal drying of agglomerates to recover the heptane and reduce agglomerate moisture whereas the diesel process relies on mechanical removal of water. Therefore, the water content of the product of any heavy oil process will be higher than that of a light oil process, given the same feed coal grind. Technical Considerations High-shear bench-scale tests indicate little, if any, difference in the efficiency of pyritic sulfur rejection between the two processes. Optimization of high-shear mixing conditions for each process has resulted in a 10-15% improvement in pyritic sulfur rejection. The heptane high-shear operation was improved by a reduction in the feed slurry solids concentration. The diesel high-shear operation was improved by making changes in the mixing energy intensity and residence time. The variables and conditions tested and the process conditions selected for each process are summarized In Tables 4 and 5. Table 4 HEAVY-OIL PROCESS OPTIMIZATION Variables Tested Agglomerating liquid Agglomerant dosage Particle size High-shear solids HS residence time HS mixing intensity Microagglomerate recovery Flotation solids Flotation stages * M-D: Maya-Diesel; FO-D: Fuel Oil-Diesel Conditions Tested Diesel, Maya, M-D, FO-D* 0.5, 3, 6, 10% 28M, 100M, 200M 5, 10,20% 0.5, 1, 2, 4 minutes 1600, 2000, 2400 rpm Screening, flotation 1.5,3,6% 1-stage and 2-stage Table 5 LIGHT-OIL PROCESS OPTIMIZATION Variables Tested Agglomerating liquid Agglomerant dosage Particle size High-shear solids HS residence time HS mixing Intensity Microagglomerate recovery Conditions Tested Hexane and Heptane 10,20,30,50,100,150% 28M, 100M, 200M 5, 10, 15, 20% 0.5, 1, 2, 4 minutes 1600, 2000,2400 rpm Screening, flotation Selected Levels Diesel 1% 28M/100M 20% 1 minute 1600/2000 rpm Flotation 6% 2-stage Selected Levels Heptane 10-30% 200M 5% 1 minute 1600/2000 rpm Screening Since the pyritic sulfur rejection efficiency of the two processes is not significantly different, evaluation of other factors will be critical in order to choose the best process option for continued work and eventual commercialization. An economic assessment of the two processes at the 200-t/h scale is underway. Preliminary results indicate that the higher capital cost of the heptane process, due primarily to the cost of the heptane recovery system, is offset by the higher operating cost of the diesel process, due to the amount of oil which is left in the product. Important criteria for process selection are shown below: 9 |