Oxy-combustion of liquid fuel in an ion transport membrane reactor

Int J Energy Environ Eng DOI 10.1007/s40095-017-0246-4 ORIGINAL RESEARCH Oxy-combustion of liquid fuel in an ion transport membrane reactor Rached Ben-Mansour1,2 • Pervez Ahmed1,2 • Mohamed A. Habib1,2 Aqil Jamal3 • Received: 14 June 2017 / Accepted: 11 September 2017 Ó The Author(s) 2017. This article is an open access publication Abstract The present work aims at investigating oxy-fuel combustion of liquid fuels in a concentric parallel tube oxygen transport reactor (OTR) using BSCF ion transport membrane (ITM) for oxygen separation. A computational model was developed and validated utilizing the available experimental results. It is assumed that the same model will be sufficient to capture reasonable results with liquid fuel oxy-combustion. The use of ITMs to produce oxygen for the conversion of liquid fuels into thermal energy in an oxygen transport reactor (OTR) while capturing CO2 is presented. In this case, the OTR has two functions: O2 separation and reaction of evaporated liquid fuel with oxygen. A parametric study of the influence of parameters such as oxygen pressure in the feed and the permeate sides on the performance of the OTR is conducted. The effect of the rates of the feed flow and sweep flow on the permeation of oxygen permeation has been evaluated. Subsequently, the effects of flow rates of feed and sweep on temperature and reaction characteristics are also explored. The optimal flow rates and flammability limits for the present geometry model to obtain maximum output are suggested. The feasibility of using liquid fuels as potential fuel to be used in near future oxygen transport reactors is presented. Keywords Liquid fuels  BSCF  Ion transport membranes  Oxygen separation and combustion List of symbols Acell Area of the cell (m2) a Absorption coefficient Cp Heat capacity (J/kg K) Di;m Diffusion coefficient of mixture species i (m2/ s) Dv Diffusion coefficient of oxygen vacancies (cm2/s) Di;j Binary mass diffusion coefficient of species i (m2/s) ED ; Er ; Ef Activation energies (J/kg-mol) I Radiation intensity, which depends on position and direction JO2 Oxygen permeation flux (mol/m2 s) kr Surface exchange reaction reverse-rate constant (mol cm-2s-1) kf Surface exchange reaction forward-rate constant (cm atm-0.5s-1) L Membrane thickness (m) n Refractive index p Pressure (Pa) 0 Partial pressure of oxygen at the feed side (Pa) PO , P1 2 00 PO2 ,P2 ! & Mohamed A. Habib 1 KACST-TIC #32-753, KACST, Dhahran, Saudi Arabia 2 Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia 3 Saudi Aramco, Dhahran 31261, Saudi Arabia r Si, Sm ! !0 s, s T U, V Vcell Partial pressure of oxygen at the permeate side (Pa) Position vector Source/sink term (Kg/m3 s), mass source term (Kg/m3 s) Direction vector, scattering direction vector Temperature (K) Superficial velocity (m s-1) Volume of cell (m3) 123 Int J Energy Environ Eng Xi Yi ui;j / 0 X q l lO2 rs r Mole fraction of species i (-) Mass fraction of species i (-) Mixture rule constant for species i in species j (-) Phase function Solid angle Density (Kg m-3) Dynamic viscosity (N s m-2) Oxygen vacancy potential (J/mol) Scattering coefficient Stefan–Boltzmann constant (5.669 9 10-08 W/m2 K4) Introduction Many studies in the past have been conducted to evaluate the feasibility of using reactors comprising ion transport membrane for the oxy-fuel combustion applications with gaseous fuels [1, 2]. However, to the author’s knowledge there are no studies on utilizing liquid fuels for the same application. CO2 emissions from combustion of fossil fuels in many industries pose a serious threat to the environment. Several CO2 capture technologies [3, 4] are now available, out of which membrane technology appears promising and has the potential to capture CO2 efficiently. A considerable progress in the application of ion transport membrane technology in the area of gas separation in industry is achieved [5]. In the past, pressure swing adsorption and cryogenic distillation presented conventional ways for the separation of oxygen from air. During the past 20 years, oxygen separation from air utilizing ion transport membranes has shown a considerable progress. This technology offers significant advantages over conventional means through the reduction of energy requirements, operational, and capital costs. Accordingly, it leads to a better plant efficiency. The use of ceramic based membrane technology is expected to gain much commerciality in the near future due to its promising potential for a better and clean environment [6]. In recent decades, the ionic/electronic conducting membranes were used in the process of oxygen separation from atmospheric air in coal gasification plants and power generation cycles utilizing the oxy-fuel combustion technology. Integrating dense mixed-conducting membranes (MCMs) into power cycles with CO2 capture has been considered as the most advanced technology for high efficiency and clean power production. Membrane separation plays an important role in these technologies for CO2 reduction. Especially, the dense mixed-conducting membranes (MCMs) have shown some possibilities of implementation in power generation plants because of their 123 better thermal and chemical stability, and typically higher selectivity [7]. Dense perovskite membranes demonstrate high oxygen ion permeability when subjected to an oxygen partial pressure gradient at high temperatures [8–10]. Moreover, the use of ITMs for oxygen separation comes with a penalty of relatively small pressure drop across the unit compared to the existing cryogenic process. It may be noted here that integrating ITMs with a power plant still faces many challenges and operational constraints that needs to be addressed. ITM units operate at elevated temperatures [11], and are mostly depends on O2 partial pressure difference across the membrane for separation process [12]. In order for the cost of ITM to be reduced and their commercialization to be feasible, next generation ITMs should achieve high permeation fluxes while operating at low temperatures. The aforementioned approaches for ITMs, if developed successfully can commercialize ITM reactor systems [13]. However, important process parameters including ion exchange at the surface, diffusion in porous media and mass transfer either by convection or diffusion should not be neglected [14]. Other expressions such as mixed conducing membranes (MCM), and oxygen transport membranes (OTM) are also used for ion transport membranes [7]. Ion transport membranes (ITMs) are composed of different inorganic compounds combinations. These compounds have a perovskite or fluorite configured crystal lattice structure [15]. The utilization of membranes in gas or air separation processes is expected to increase to five times of its current value by 2020 [16]. Many studies are presently performed to enhance their chemical stability as well as gas (...truncated)