Process Simulation for Biofuels Production from Castor Oil

Abstract

In this study, the process simulation for producing biofuels from castor oil was developed with remarkable success. The objectives were to simulate the mass and energy balance for different catalysts consisting of Alumina and Nickel composites at various temperatures and pressures, with applicable conversion rates. The Alumina catalyst was used for hydrotreating at 345˚C and 30bar for green diesel production and hydrocracking at 240˚C and 60bar for bio-jet fuel and bio-gasoline production. Nickel-based 25%NiSAPO-11 was used for the hydrotreating process at 300˚C and 30bar, 25%Ni/ZSN5 was used in the hydrocracking process at 300˚C and 30 bar for bio-jet fuel and bio gasoline production. Green diesel was produced from the two catalysts with a similar flowsheet. The quality of the green diesel is aligned with the commercial diesel and thus provides confidence for the green diesel to be produced commercially. There are tail gases produced as waste streams during this process, which can be environmentally unfriendly; however, their impact is less than that of using fossil fuels for fuel. The tail gas contains carbon dioxide, which is a greenhouse gas. Carbon capture and storage technology can be used to store the gas and eliminate negative environmental impact. The carbon capture technology is not covered in the study. Based on the results, the green diesel process was scaled up in mass flow to larger larger sized process plant without any complications. The scaling is proportionate in nature to the ratio of the pilot initially studied. Product qualities remain the same, and the demand for feedstock and energy scales in proportion to the castor oil feed rate. The waste streams are also proportionate. Hydrogen as a feedstock is consumed in the process; the production process for hydrogen was not explored, although the use of green hydrogen in the process would be ideal. The energy requirement for the green diesel process is for the hydrogen compressor, which generates elevated temperatures for the hydrotreating reactor. In this study, the green diesel flowsheet was further developed to produce bio-jet fuel in the hydrocracking reactor. With the application of Alumina catalyst and 25%Ni/ZSN, these processes were developed first for the 100kg/hr of castor oil and then for the 1000kg/hr of castor oil feed. In addition, the process flowsheets were identical, with a variation in process reactor conversions, pressure, and temperature conditions. The Bio jet fuel was produced through green diesel cracking with hydrogen, forming short alkanes. The products were separated in a RadFrac distillation column. The Bio-jet fuel was the heavy fraction of C8 to C15, and the light liquid hydrocarbons streams were the top products. The bio-jet fuel produced was compatible with commercial jet fuel, which can thus be produced for commercial applications. The energy consumption of the bio-jet fuel is in addition to the green diesel process, although energy recovery is possible through process integration between the heaters and coolers. Pinch technology principles were applied in the integration of the process streams. There was a hydrogen compressor installed for the supply of hydrogen into the cracking process. A turbine was installed to recover the unreacted hydrogen and gases, integrating them into the green diesel process. Based on the results, the bio-jet fuel process was scaled up without compromising the product quality. The hydrogen recovery process was integrated with the green diesel hydrogen system. The bio-gasoline production process was achieved through optimisation of the separation section of the bio-jet fuel production process. The hydrocracking reactor produces a varied range of hydrocarbons from C3 to C16, and the bio-gasoline was composed of C4 to C12. Therefore, various distillation optimisations can be embarked on to determine the product slate for either bio-jet fuel or bio-gasoline. Bio-jet fuel composition includes C7 to C15 components. The bio-gasoline process also produced petroleum gas as a byproduct. In the RadFrac column separation stage, bio-gasoline was produced as a bottom’s product, and the top products were liquid and gas streams. These top streams had comparable properties to petroleum gas with high percentages of propane and traces of butane. Residual hydrogen from the hydrocracking reactor also appeared in the gaseous stream.