Determination of the kinetics of hydrogasification reactions and evaluation of various extraction schemes used in recovery, regeneration and recycle of spent eutectic catalysts

The two topics that are addressed in this present work are hydrogasification of Illinois #6coal using a ternary (43.5 mol% Li₂CO₃-31.5 mol% Na₂CO₃-25 mol%K₂CO₃) and a binary (29 mol% Na₂CO₃-71 mol%.K_{2CO3) eutectic catalyst system and the recovery and regeneration of the spent catalysts present in the gasified char obtained after gasifying the coal with steam. Hydrogasification experiments were carried out in a high-pressure,high-temperature differential fixed-bed gasifier unit to evaluate the product inhibition effect of H2 on the steam gasification kinetics. The gasification fate was found to decrease with an increase in the H2 partial pressure. A rate expression of the Langmuir-Hinshelwood type was used to satisfy the experimental data at different H2 partial pressures and based on this model a possible reaction mechanism was proposed. A Detailed study is recommended to evaluate the effect of other product gases like CO andCO2 on the reaction kinetics. The work on catalyst recovery and regeneration involves evaluating the effects of various process variables such as solvent-to-char ratio, mixing time and temperature on the extraction efficiency. ,In addition to this, various extraction schemes using water, sulfuric acid and acetic acid were compared with respect to their extraction efficiencies. While the solvent-to-char ratio and mixing time had negligible effect on the catalyst recovery, the recovery increased with increase in temperature.Sulfuric acid and acetic acid were found to be much better solvents than water. A comparison of the stand alone catalyst recovery ^d regeneration plant cost for a ,100MWt catalytic coal gasification plant for the three extraction schemes and the once-through process showed that the sulfuric acid extraction is most economical. A multistage extraction scheme is recommended to make the process more attractive.}