(42a) Molecular Modelling of Co-Processing Biomass Pyrolysis Oil with Vacuum Gasoil in an Oil Refinery Fluid Catalytic Cracking Unit

Integration of renewable resources in petroleum refining has been a research focus for several years. It is becoming a priority for several developed countries, especially in Europe and North America, to increase the share of renewable energy sources in their transportation fuel system. For example, EU’s members countries aim to increase renewables contribution from the current value of 7.1% to 10% by 2020 [1] .

Several works try to find optimum integration points within transportation fuel system [2], while other researches focus on assessing the viability of different renewable sources. Recent works have been focusing on the integration of second generation biomass feedstock in petroleum refining. This is mainly due to the fact that second generation biofuels do not create competition with food industry and satisfy the criteria published in Article 17 [3] .Two types of processes are suggested, namely gasification and pyrolysis. This research is concerned with the second alternative since it allows the assessment of several integration options within conventional petroleum refinery for the bio-liquid asset produced.

Bio oil produced from pyrolysis processes is considered as a candidate for co-processing with heavy petroleum fractions in refinery catalytic conversion processes [4], such as catalytic cracking and hydroprocessing units. Careful assessment of the effects of introducing bio oil to refinery processes is required.

In this work, a novel methodology is developed to investigate the effect of introducing bio oil to the feed of the fluid catalytic cracking units on product yields and properties especially gasoline and diesel. The proposed method includes detailed, molecular-level characterisation of feed and product streams based on Molecular Type and Homologous Series matrix (MTHS) approach, as well as detailed reaction network and kinetic models which take into account the complex interactions between the various molecular attributes. Kinetic parameters is tuned through an optimisation problem in which the objective function is to minimise the difference between measured and predicted products yields at various conversion levels. The capability of the proposed methodology is demonstrated using a case study for the characterisation of vacuum gas oil (VGO) and fast pyrolysis oil (FPO) blend which is used as a feed for fluid catalytic cracking process (FCC) [5]. There are 328 reactions that are used for the synthesis of the reaction network. The computational results demonstrate that an overall good agreement between measured and predicted yields is obtained using the developed kinetic model for VGO: FPO blending ratio, C/O ratio and reaction temperature of 95:5, 5 and 530°C, respectively [6]. PONA composition in each layer of product stream (e.g. gasoline, diesel, gasoil, etc.), as well as oxygen compounds compositions and oxygen content in each product fraction is predicted using the developed models.

This creates potentials for rigorous optimisation of process parameters for refinery process maximisation or better products’ quality control. The methodology developed in this work can easily be extended for the modelling of other refinery processes. This will help in rigorously evaluating different integration options of biomass pyrolysis oil into conventional refinery, and will help into integrating the developed reaction models into dynamic models for refinery’s hydrogen network in order to optimise hydrogen consumption. Finally, the success of this approach can revolutionise refinery processes’ design methodologies and optimise the integration of renewable resources, such as biomass, into transportation fuels system.

KEYWORDS: Catalytic cracking, Fast pyrolysis oil (FPO), biomass, refinery, MTHS matrix, Vacuum gas oil (VGO)

[1] The European Commission, “Renewable energy statistics,” 2015. [Online]. Available: http://ec.europa.eu/eurostat/statistics-explained/index.php/Renewable_en.... [Accessed: 01-Jun-2017].

[2] S. Jones et al., “Process Design and Economics for the Conversion of Lignocellulosic Biomass to Hydrocarbon Fuels Fast Pyrolysis and Hydrotreating,” PNNL Rep., vol. PNNL-23053, p. 97, 2013.

[3] European Commission, “Sustainability criteria,” 2011. [Online]. Available: https://ec.europa.eu/energy/en/topics/renewable-energy/biofuels/sustaina.... [Accessed: 25-May-2017].

[4] D. C. Elliott, “19 - Production of biofuels via bio-oil upgrading and refining BT - Handbook of Biofuels Production (Second Edition),” Woodhead Publishing, 2016, pp. 595–613.

[5] D. V Naik et al., “Catalytic cracking of jatropha-derived fast pyrolysis oils with VGO and their NMR characterization,” RSC Adv., vol. 5, no. 1, pp. 398–409, 2015.

[6] D. V Naik, V. Karthik, V. Kumar, B. Prasad, and M. O. Garg, “Kinetic modeling for catalytic cracking of pyrolysis oils with VGO in a FCC unit,” Chem. Eng. Sci., vol. 170, pp. 790–798, 2017.