| These characteristics in turn depend on the nature of the parent coal and on the devolatilization conditions. |
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| During gasification, coal initially undergoes devolatilization, and the residual char undergoes some or all of the reactions listed in the Table. |
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| First is the efficient removal of the water and carbon dioxide released during prograde devolatilization reactions by upward migration of the fluid along grain boundaries and through fractures. |
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| A portion of the volatile species may be reabsorbed and recombined onto the surface of the char matrix by the devolatilization process. |
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| These result in turn from the combination of a very large melt surface in the multi-screw section of the extruder, an intensive melt exchange and an optimum devolatilization. |
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| The recirculating oil ring pump is replacing once-through water sealed vacuum pumps to pull vacuum from extruder vents to enhance devolatilization efficiencies. |
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