Araceli Guadalupe Romero-Izquierdo

Energy integration of a hydrotreating process for the production of biojet fuel

Biojet fuel has been identified as the most promissory alternative to reduce CO2 emissions in the aviation sector, which contributes about 2% of the total emissions of carbon dioxide. There are several processes available for the production of biojet fuel; nevertheless, the hydrotreating process is one of the most promising, since it can be adapted to the existing refinery infrastructure and it is also certified by ASTM. Biojet fuel, nevertheless, is still not economically competitive with the conventional, petroleum-based jet fuel. Thereby, in this work we propose the energy integration of the hydrotreating process considering Jatropha Curcas as renewable raw material. We present a kinetic model for the reactive section, in order to estimate the energy released by the process, which is used to partially satisfy the energy requirements of the purification section. Finally, the effect of the energy integration on the price of biojet fuel is analyzed. Results show that the cost per liter of biojet fuel is very close to the cost of the fossil one, when the energy generated in the process is used. Thus, through a proper energy integration on the production process, the cost of biojet fuel can be competitive with that of the fossil jet fuel.

Modelling of the hydrotreating process to produce renewable aviation fuel from micro-algae oil

Abstract Renewable jet fuel has been identified as the most promissory alternative to reduce CO2 emissions in the aviation sector, allowing its sustainable development. This renewable fuel, also known as biojet fuel, can be obtained from different types of biomass, which include lignocellulosic biomass, sugar, starchy and triglyceride feedstock. In particular, the conversion of triglyceride feedstock to biojet fuel is realized through the hydrotreating process, where hydrodeoxygenation, hydroisomerization and hydrocracking reactions are carried out; after that, the purification of the renewable hydrocarbons is realized through distillation columns. The modelling and intensification of the hydrotreating processes have been previously analyzed for castor oil and jatropha curcas oil, which are the non-edible crops with highest productive potential in Mexico. However, another raw material with high productive potential is micro-algae oil, since it can be cultivated in non-fertile lands, avoiding the competition with food crops for ground use. Therefore, in this work we propose the modelling of the hydrotreating process to produce biojet fuel, considering micro-algae oil as raw material. The reactive section is modelled with a multifunctional catalyst; thus, all the hydrotreating reactions are carried out in one vessel. The produced renewable hydrocarbons are purified by conventional distillation sequences: direct, indirect and combined. Thus, three conventional hydrotreating processes are defined and evaluated in terms of total annual costs, CO2 emissions and price of biojet fuel. It has been found that the hydrotreating process that includes the direct conventional sequence presents the lowest total annual costs. Also, in all scenarios the biojet fuel price is competitive with the fossil one. Considering the high productivity per hectare, microalgae oil is a very promissory raw material for sustainable production of renewable jet fuel with a competitive price.

Process integration for the supercritical production of biodiesel and the production of lignocellulosic bioethanol

Abstract Biodiesel and bioethanol are among the most studied biofuels. For the production of biodiesel, the use of supercritical alcohols has been reported as an alternative with some advantages over the traditional base-catalyzed processes. Nevertheless, due to the high pressure and temperature conditions under which the supercritical process operates, the energy demand can be considerably high. On the other hand, production of bioethanol through lignocellulosic biomass is a topic of interest, because it avoids the competence with food industry derived of using first-generation biomass. In such processes, several reaction steps are required, with water as one of the main resources. Therefore, the integration of both production processes could be advantageous in terms of energy costs and environmental impact. In this work, the feasibility of mass and energy integration between the supercritical biodiesel production process and a lignocellulosic bioethanol process is evaluated, as a strategy to reduce external energy requirements and mass agents. By this approach, reductions on the utilities costs are expected if compared with the individual processes.

Feasibility of energy integration for high-pressure biofuels production processes

Abstract The production of renewable fuels has been proposed as a feasible alternative, in the short-and medium –term, to mitigate the environmental impact due to the use of fossil fuels for the transport sector. Biodiesel and biojet fuel are promising fuels to partially replace their corresponding fossil fuels. To produce biodiesel, processes with supercritical alcohols shows some advantages over the traditional base-catalyzed processes, e.g., no undesired reactions occur when the raw material has high concentration of free fatty acids. It is worth to mention that this process operates at high pressure and temperature, so the energy demand is elevated. On the other hand, the biojet fuel production through the hydrotreatment process has been developed as a feasible alternative, due to its similarity with the conventional refining processes. Like the supercritical process for biodiesel production, bio-jet fuel production requires high pressure and temperature, thus having high energy requirement. In both processes, distillation, an energy-intensive separation process, is used to generate the desired hydrocarbons fractions. Thus, to determine potential reduction in the total energy requirements for both processes, the feasibility of energy integration between the supercritical biodiesel process and the hydrotreating process to produce bio-jet fuel is studied in this work. By this approach, reductions on the utilities costs are expected if compared with the individual processes. Also, due to energy integration, which reduces the external energy requirements, global environmental impact is expected to be reduced as well.

Design of a low-cost process for the production of biodiesel using waste oil as raw material

Abstract Biodiesel is a promissory candidate to partially replace the use of fossil diesel in engines and other devices for energy production; it is composed by a combination of alkyl esters. It can be produced mainly from vegetable oils; which cost represents around 60-80% of the total production cost of biodiesel, affecting the selling price of the biofuel. Thus, the use of waste oils as raw material has been studied in the last years, because they are a cheaper alternative. However, they usually have a high content of free fatty acids, thus its conversion into alkyl esters require additional steps; since alkaline transesterification of oils with a high composition of free fatty acids is accompanied by saponification reactions. Usual pre-treatments involve the use of acid, homogeneous catalysts to transform the fatty acids into alkyl esters. On the other hand, the conversion of the oil into biodiesel is performed by reactions with alcohols, usually methanol which is produced commonly from petrochemical routes; this fact makes the production of biodiesel less sustainable. An alternative alcohol to produce biodiesel is ethanol, which can be obtained from other bioprocesses. In this work, the design of a low-cost biodiesel production process is reported, using waste cooking oil as raw material. Simulations of the process are performed in the process simulator Aspen Plus. Sensitivity analysis are performed to the equipment with degrees of freedom, to determine the design with the lowest energy requirement. Total annual costs and environmental impact are evaluated for the process.

Modeling, simulation and intensification of hydroprocessing of micro-algae oil to produce renewable aviation fuel

Micro-algae are photosynthetic organisms, which represent a promissory renewable raw material for biofuels production, since they can be cultivated in non-fertile lands, avoiding the competition with food crops for land use. From micro-algae, oil can be obtained oil that can be converted to biodiesel, green diesel and biojet fuel. In particular, the renewable aviation fuel is one of the less explored biofuels; nevertheless, for the aviation sector, this is the best alternative to reduce CO2 emissions, allowing its sustainable development. In order to produce hydrocarbons in the boiling point range of jet fuel, we need to transform the micro-algae oil. A number of research projects report the use of micro-algae oil for the production of biojet fuel through the hydrotreating process. However, the application of process intensification strategies for the hydroprocessing of micro-algae oil has not been reported. Therefore, in this work we propose the modeling, simulation and intensification of the hydrotreating process to produce biojet fuel, considering micro-algae oil as raw material. The hydroprocessing of micro-algae oil is modeled in Aspen Plus processes simulator, based on data from an experimental study recently reported. The produced renewable hydrocarbons are purified through conventional and intensified distillation sequences; thereby, conventional and intensified hydrotreating processes are defined and evaluated in terms of total annual costs, CO2 emissions and biojet fuel price. Simulation results show that the implementation of intensification strategies leads to the production of biojet fuel with reduced carbon dioxide emissions, 34% less, and a competitive price per liter, 78% cheaper than fossil jet fuel price.

Energy Integration and Optimization of the Separation Section in a Hydrotreating Process for the Production of Biojet Fuel

Abstract In the transport sector, aviation has a strong growing, expecting an annual increase of 5% with respect to other transport ways. If fuel consumption grows at the same rate, CO 2 emissions due to worldwide aviation in 2050 would be more than six times of the current value. The International Civil Aviation Organization has recognized sustainable alternative fuels, such as biojet fuel, as an important pillar to strategically reduce greenhouse gas emissions from aviation. There are several pathways potentially suitable to produce biojet fuel. Nevertheless, the hydrotreating process is one of the most promissory; its main challenges are the reduction of the investment and operation cost, along with the selling price of biojet fuel. Thereby, in this work the modelling and optimization of the separation zone of the hydrotreating process for the production of biojet fuel are presented, considering Jatropha Curcas oil as renewable raw material. In the separation zone four distillation schemes are considered; two conventional and two intensified options. They were optimized by a multi-objective genetic algorithm accelerated by neuronal networks; generating a Pareto front for each scheme, showing the better trade-off between the two objectives: number of stages and reboiler duty. For each scheme a point from the Pareto front is selected, which is integrated to the reactive zone of the previously modeled process in order to estimate the energy released for the whole process. The results show that it is possible to satisfy some of the energy requirements of the purification zone through energy integration. Also, the process with the direct conventional distillation sequence has the lowest energy consumption; having a direct impact on the cost of biojet fuel, which results competitive with that of the fossil jet fuel.