Faculty of Technology, University of Tuzla, Tuzla, Bosnia and Herzegovina, Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, United States, Faculty of Chemistry and Chemical Engineering, University of Maribor, Maribor, Slovenia, Swiss Federal Institute of Technology Lausanne, Lausanne, Switzerland, Sustainable Process Integration Laboratory—SPIL, NETME Centre, Faculty of Mechanical Engineering, Brno University of Technology—VUT BRNO, Brno, Czechia, CanmetENERGY, Natural Resources Canada, Varennes, QC, Canada, School of Chemical Engineering, Dalian University of Technology, Dalian, China

This work presents the synthesis of heat-integrated water networks (HIWNs) by using mathematical programming. A new superstructure is synthesised by combining a water network and a modified heat exchanger network. Based on the proposed superstructure, a mixed-integer nonlinear programming (MINLP) model is developed. The model is solved by using a one-step solution strategy enabling different initialisations and the generation of multiple solutions, from which the best one is chosen. The results show that the proposed model can be effectively used for solving HIWN problems of different complexities, including large-scale problems.

Abstract To comply with the outcomes of the Climate Change Conference in Paris (COP 21), the ever-growing greenhouse gas (GHG) emissions has to be drastically reduced. With the soaring growth rates of GHG emissions in the aviation sector, the need for a near zero-net greenhouse emission alternative is essential. The novel concept of the Power-to-Jet pathway directly utilizes renewable electricity, carbon dioxide and water to synthesize a sustainable kerosene fuel that chemically resembles the one produced from fossil sources, having ‘Drop-in’ capability allowing the use and distribution within existing architectures. In the Power-to-Jet process, hydrogen is produced via water electrolysis. Captured CO2 (from rich point sources) then reacts with hydrogen to produce the intermediate methanol, before being upgraded to the final synthetic jet fuel along with by-products (Schmidt et al., 2012). With fluctuating electricity inputs due to the variability in photovoltaic and wind power generation, the process units within the Power-to-Jet process have to be adjusted at each time-instant to satisfy the production constraints. To find the best operating strategy for these fluctuating conditions, dynamic models are needed. In this work, we will propose a model that describes the dynamic behaviour of the carbon capture section in the Power-to-Jet process. Several dynamic scenarios can be introduced for the carbon capture rate by altering the lean solvent concentration, flue gas flow rates and re-boiler duty. The dynamic information obtained from the simulations (such as: Open loop gain, time constants and dead time) can be used to device an appropriate control scheme under varying electricity inputs, while satisfying all operational constraints.

Abstract A synthesis of an industrial utility system considering cogeneration options together with heat exchanger network synthesis has been developed. It consists of boilers at different temperature and pressure levels, steam turbines, condensers, cooling tower, deaerator and a heat exchanger network system, connecting the utility system with the process heat and electricity requirements. A mixed-integer nonlinear programming (MINLP) model was used for synthesis. A sensitivity analysis has been performed considering the price ratio of natural gas to electricity, while also estimating primary energy consumption and GHG emissions. The results indicate that the cogeneration is economically viable at different ratios of natural gas and electricity price. In addition, the sensitivity analysis shows the relationship between cogeneration and electricity purchase for obtaining the minimal primary energy consumption and consequently to reduce GHG emissions.

Abstract The fluctuating production of renewable energy constraints the operation of Power-to-X processes such that steady-state conditions are unattainable without energy storage. It seems eminent to establish operation strategies considering significant disturbances along the process and to determine those scenarios where the operation becomes unfeasible. In this work, an industrial methanol Lurgi-type reactor, embedded in a Power-to-Jet process (Figure 1), is evaluated under fluctuating feed conditions. The simulated scenarios consist of step functions up to 20 % (w/w) increments in the feed flowrate as consequence of the fluctuating power input on the electrolysis stage. A one-dimensional dynamic model for a multi-tubular fixed bed reactor is implemented, considering both the gas and catalyst phase. The mathematical model is solved numerically using orthogonal collocation at the spatial domain and backward differences at the time domain. The system shows rapid response to disturbances, reaching steady state conditions in 1.5 minutes. Furthermore, it is evidenced that the feasible region to increase the production of methanol is narrowed down by rises of carbon dioxide feed flowrate up to 5 % (w/w).