Seiya Hirohama

Distribution function model for deep desulfurization of diesel fuel

We attempt the optimum design of the ultra-deep hydrodesulfurization required in the future or for the hydrogenation of aromatics in diesel oil, as the conventional reaction model based on n-th order of desulfurization is no more accurate enough. A further buildup of reaction simulator for reactor design was attempted. Distribution Function Model is developed in the present study. In this model, the distribution of rate constants is expressed with a Γ function. It is clear that the predictions agreed well with the observed data, down to the ultra-deep desulfurization range. This model could also be applied for various kinds of oil fractions and wide desulfurization reaction conditions. The reactor sizes were estimated, compared with both the distribution function and n-th order reaction models, in order to obtain diesel oil of sulfur level required by European Auto-Oil II Program. The reactor size calculated by the Distribution Function Reaction Model is estimated as being smaller than that estimated by the conventional 1.7th order. It means that a more competitive design of the process will be provided by the new model and will allow more practical feasibility study and the plant design for ultra-deep desulfurization process.

Citric acid purification process using compressed carbon dioxides

Abstract Citric acid (CA) has successfully been separated from fermentation broth by a novel and unique purification process, which is characterized by organic solvent extraction and precipitation with compressed carbon dioxide (CO 2 ) as a poor solvent. After the filtration of microorganisms, the condensed fermentation broth of CA was dissolved in acetone. In this extraction, a certain amount of impurities (mainly sugar) could be separated as precipitates. Compressed CO 2 was then dissolved in the acetone solution of crude CA to remove the residual impurities as precipitates using the anti-solvent effect of CO 2 . The deposited impurities were readily separated from the acetone solution of CA by a settler. Finally, food additive grade CA was easily obtained by simple decolorization and crystallization methods. Also, CA crystals could be obtained by the anti-solvent crystallization with CO 2 . crystallization with CO 2 .