MODELING OF ASPHALTENES AND OIL SHALE PYROLYSIS F. Munoz 2 , S. Dhir 1 , J. P. Mmbaga 1 , R. Gupta 1 , R. E. Hayes 1 , M. Toledo 2 1. University of Alberta, Edmonton, AB Canada. 2. Departamento de Ingeniería Mecánica, Universidad Técnica Federico Santa María, Valparaiso, Chile Objective • Integrate Grain model along with COMSOL Multiphysics to study the effect of processes occurring in pyrolysis. • To study the effect of particle size and process temperature. • To study the effect of organic matter content in oil shale. • Explore limitations of diffusion and convection in pyrolysis process. Governing Equations • Momentum transfer equation in gas ρ u t +ρ u∙ u =∙ −pI + μ u + u T − 2 3 μ ∙u I +F • Equation of continuity   +∙  =0 • Heat transfer in gas ρc p T t + ρc p u ∙ T =  ∙ kT + Q + Q vh • Darcy’s law u= K p μ P • Permeability of asphaltenes K p =D p 2 ∗ ϵ 3 150 ∗ (1 − ϵ) 2 • Reaction r i =kc i Modeling Framework Define Model Non-Isothermal fluid Transport of Concentrated Species Species transport in porous media Heat transfer in porous media Fig 1: Simplified modeling approach Assumptions: • The heavy oil drop is considered static inside of the cylindrical furnace. • The heavy oil drop is considered as a porous media with a constant size and porosity variation, following a grain model. • An initial temperature of 300K is considered for heavy oil drop. • The initial temperature inside the cylindrical drop tube furnace proposed will be same as that of the boundary condition (wall temperature). • Nitrogen is used as a sweeping gas through the furnace. Nitrogen sweep Surface heating Introduction The world mainly focusses on the fossil fuels for energy and transportation needs with oil being the main source along with coal. With high demand and high prices of conventional oil the present research has been focused on energy generation from oil shale and asphaltenes. Pyrolysis is the primary step in gasification process which involves formation of syngas that is valuable in energy production as well as synthesis of fuel and chemical. Effect of parameters like size, organic content, porosity play an important role during pyrolysis condition. Discussion 0 0.2 0.4 0.6 0.8 1 0 10 20 30 40 50 60 Isothermal Pyrolysis of Asphaltene - r = 0.02 [cm] %Weight, Tw = 700 [K] %Weight, Tw = 800 [K] %Weight, Tw = 900 [K] %Weight Time [s] 300 400 500 600 700 800 900 0 10 20 30 40 50 60 Asphaltene Temperature Profile - r = 0.02 [cm] Tw = 700 [K] Tw = 800 [K] Tw = 900 [K] Temperature [K] Time [s] 0 0.2 0.4 0.6 0.8 1 1.2 0 5 10 15 Isothermal Pyrolysis of Asphaltene - Tw = 850 [K] %Weight, r = 0.01 [cm] %Weight, r = 0.015 [cm] %Weight, r = 0.02 [cm] %Weight, r = 0.025 [cm] %Weight, r = 0.03 [cm] %Weight, r = 0.035 [cm] %Weight Time [s] Fig 2:Mass fraction of volatile at 20 s Fig 3:Mass fraction of volatile at 50 s Fig 4:Decomposition of Asphaltenes at various wall temperatures Fig 5:Asphaltenes temperature at various wall temperatures Fig 6:Decomposition of Asphaltenes at various sizes 0 0.2 0.4 0.6 0.8 1 1.2 0 5 10 15 Asphaltene Conversion - Tw = 850 [K]; r = 0.02 [cm] N2 = 0 [m/s] N2 = 0.1 [m/s] N2 = 0.2 [m/s] N2 = 0.3 [m/s] Conversión [-] Time [s] Fig 7:Asphaltenes conversion at various flow rate Conclusion • For both asphaltenes and oil shale a higher conversion rate is achieved with increase in temperature and decrease in particle size. • Asphaltenes decomposition is less compared to oil shale with temperature increase. • With increase in organic content the decomposition time for oil shale increases. • High porosity is achieved with increase in organic content thus getting less char at the end of pyrolysis. • Different flow rates of nitrogen doesn’t cause significant variation in conversion, it only affects the residence time. • Weight percent profile for isothermal condition can be validated with the literature. References [1]Torrente M.; Galan M. “Kinetics of the thermal decomposition of oil shale from Puertollano” ELSEVIER, Fuel 80, 2001, 327-334. [2]Mahapatra N.; Kurian V.; Gupta R. “Study of char obtained during the fast pyrolysis of Oil Sands Asphaltenes” Department of Chemical & Materials Engineering, University of Alberta, Edmonton, AB, Canada, 2013. [3]Tiwari P.; Bauman J.; Deo M. “Mathematical modeling of Oil Shale Pyrolysis” Petroleum Research Center, Department of chemical engineering, University of Utah, 2011. [4]Diallo M.; Cagin T.; Faulon J.; Goddard W. “Thermodynamic properties of asphaltenes: A predictive approach based on computer assisted structure elucidation and atomistic simulations. Chapter 5.Asphaltenes and asphalts, 2. Developments in Petroleum Science, 40 B [5]Aprameya Ambalae, Nader Mahinpey and Norman Freitag, “Thermogravimetric studies on pyrolysis and combustion behaviour of a heavy oil and its asphaltenes” , Energy and Fuels , 2006, 20, 560-565. 0 0.2 0.4 0.6 0.8 1 0 10 20 30 40 50 60 Oil Shale Porosity - r = 0.02 [cm]; Om = 35% Tw = 700 [K] Tw = 800 [K] Tw = 900 [K] Porosity [-] Time [s] 0 0.2 0.4 0.6 0.8 1 1.2 0 5 10 15 Isothermal Oil Shale Pyrolysis - Tw = 850 [K] ; r = 0.02 [cm] %Weight, Om = 35% %Weight, Om = 60% %Weight, Om = 85% %Weight Time [s] 0 0.2 0.4 0.6 0.8 1 0 5 10 15 Oil Shale Porosity - Tw = 850 [K] ; r = 0.02 [cm] Om = 35% Om = 60% Om = 90% Porosity [-] Time [s] 0 20 40 60 80 100 120 0 200 400 600 800 1000 % Weight Temperature[K] Literature comsol Fig 8:Porosity variation of Oil shale at various wall temperatures Fig 9:Decomposition of Oil shale Fig 10:Porosity variation at various organic content Fig 11: Validation of TGA profile Excerpt from the Proceedings of the 2014 COMSOL Conference in Boston